Creating Multiple Sequence Alignments by 6Z5NvUA

VIEWS: 13 PAGES: 12

									                                     BIT150 – Lab3
  Sequence Alignment, Multiple Sequence Alignment and Phylogenetics
Copy 10_Lab3 from Z: to C:.

A. SEQUENCE ALIGNMENT
The most basic task in sequence analysis is to ask whether two sequences are similar and
can be compared. Proteins with very similar sequences probably share structural
properties and similar functions.

Objective: Explore different methods of sequence alignment, interpret their results, and
compare them.

A1. Graphical method
Dotter (http://www.cgb.ki.se/cgb/groups/sonnhammer/Dotter.html ): A dot-matrix
program with interactive grayscale for DNA and protein sequence analysis.

 Dotter is preinstalled on your lab computers.
  Follow these steps to run Dotter:
   1.1. The DNA sequence file WIS.txt to be used with Dotter is in ‘10_Lab3\Dotter
   files’. Copy this file into the ‘C:\BIT150\Programs\Dotter’ (an alternative is to write
   the PATH of each file when you run the program).

     1.2. Dotter needs to be started from the Command Prompt window:
     Start-> Programs -> Accessories -> Command Prompt (create a shortcut in your
     desktop).
     Alternatively, Start -> Run… -> in Open, type cmd -> OK.
     This is the old DOS operating system (case insensitive).

     1.3. Move to the Dotter directory (located in ‘C:\BIT150\Programs\Dotter’), typing:
     call C: -> press Enter;
     cd BIT150\Programs\Dotter (to change directory).
     To see the files present in the Dotter directory, type dir. Check for WIS.txt and
     MITE2.txt.

     1.4. Using Dotter, align the DNA sequence of the retroelement WIS, WIS.txt, with
     itself to look for internal repeats. To do it, type:
     dotter WIS.txt WIS.TXT -> press Enter -> wait….

     1.5. Analyze the Dotter output:
           Dotter window: The first sequence runs along the x-axis and the second
          sequence along the y-axis. Segments of 25 bp in one sequence (along the X axis) are
          compared to segments of 25 bp in the second sequence (Y axis). In regions where the
          two sequences are similar to each other, a row of high scores runs diagonally across
          the dot matrix.




                                                                                                 1
             o Set width of the sliding window: (right click on the Dotter window and select
                  ‘Change size of sliding window’). The default width of 25 residues over which
                  the pairwise scores are averaged has proven to be very robust, but you can
                  change the width of the sliding window.
             o Print to a file: (right click on the Dotter window and select ‘Print’). You can
                  print the alignment to a PostScript file and later convert it to PDF.
            Greyramp Tool window: Generates windows along the diagonals, and draws a
           dot in the center of the window only if the sum of the scores of all ‘dots’ within that
           window is above the maximum threshold, while dots below the minimum threshold
           get the minimum intensity, and dots in between are ‘rendered’ with a grayscale
           intensity proportional to their sum of scores. Interactive and dynamic changing of
           maximum and minimum thresholds allows the exploration of various signal
           stringencies.
            Alignment Tool window: Allows you to see the match that causes a given dot in
           the dotplot. Move the crosshair of the Dotter window with the left mouse button to the
           dot, and pop up the Alignment Tool. Once in the proximity, use the cursor keys to
           move the crosshair one residue at the time.

       - Copy and paste the alignment into your Word document (use Shift/PrintScreen to
       copy all what you have in your screen, open Start/Programs/Accessories/Paint,
       paste the image, select what you want, cut it, and finally paste it into your Word
       document).
       - After aligning WIS.txt with itself, what type of repeat is present in the sequence?

A2. Dynamic-programming methods
 Global: Needleman-Wunsch algorithm (1981)
 Local: Smith-Waterman algorithm (1970)
>Seq1
ACCAACCATACGAGTATCAGACCTATCAGGCCTATCCAGAGCAGATCATGGACTAACCCTAGGACATACCATCT

>Seq2
ACTAATCATGGACTAACCCCCTAGGACATACCACTACATATGGCCTGATACCTCTGATACTCGTATGGTATCT


2.1. Open the link: http://www.ebi.ac.uk/emboss/align/
 Paste Seq1 and Seq2 into the Sequence1 and Sequence2 windows, respectively. Select
DNA as molecule where asked. Compare needle (global) and water (local) alignment
results. For both, use the default settings of Gap 10 Extend 0.5.
NEEDLE - GLOBAL
Seq1                1 ACCAACCATACGAGTATCAGACCTATCAGGCCTATCCAGAGCAGATCATG           50
                                                    .|||          ||||||
Seq2                1 ------------------------------ACTA----------ATCATG           10

Seq1               51 GACTAA--CCCTAGGACATACCATCT------------------------           74
                      |||||| ||||||||||||||| ||
Seq2               11 GACTAACCCCCTAGGACATACCA-CTACATATGGCCTGATACCTCTGATA           59

Seq1               74 --------------       74

Seq2               60 CTCGTATGGTATCT       73

WATER - LOCAL
Seq1               32 CTATCCAGAGCAGATCATGGACTAA--CCCTAGGACATACCA          71
                      |||          |||||||||||| |||||||||||||||
Seq2                2 CTA----------ATCATGGACTAACCCCCTAGGACATACCA          33




                                                                                                 2
A3. Words methods (heuristic)
 BLASTN: The Basic Local Alignment Search Tool (BLAST) finds regions of
local similarity between sequences.

   3.1. Using BLAST 2 Sequences
   (http://www.ncbi.nlm.nih.gov/blast/bl2seq/wblast2.cgi), run the same two sequences,
   Seq1 and Seq2 from 1.6. Select blastn as ‘Program’.

                                     - Copy and paste the Dot Matrix View and the
                                     alignment into your Word document.

                                     - What is the orientation of the conserved segments?

                                     - Compare this alignment with those previously
                                     obtained using, needle (global), and water (local).
                                     BLAST is more flexible to find inverted segments!

                                     3.2. Change ‘gap open penalty’ from 5 (default) to 3.
                                     Run.

        - Copy and paste the alignment into your Word document (use
        Shift/PrintScreen).
        - What types of repeats present in the sequences can you identify now?

   3.3. Which of the three methods (needle (global), water (local), BLAST 2 Sequences)
   detected better the similarities observed in Dotter?

 BLASTX: DNA-protein alignment (protein database using a translated nucleotide
query).
   3.4. Using BLAST 2 Sequences, compare the genomic DNA sequence of the Acyl
   Co-A Synthetase from Lab1 with the predicted protein sequence. Sequences are in the
   file 10_Lab1\Sequin Acyl Co-A Synthetase\ Final annotation.doc. and also in
   10_Lab3.
   Paste the Acyl Co-A synthetase DNA sequence in the Sequence 1 window and the
   Acyl Co-A synthetase protein sequence in the Sequence 2 window. Select blastx as
   ‘Program’.
        - Could you identify the 6 exons?
        - Are the borders of the exons as precise as in the flat file prepared using Sequin?

   3.5. Change ‘gap extension penalty’ from 1 (default) to 2.

       - Can you see any improvement?




                                                                                           3
 BLASTP: Comparing two proteins.

   3.6. Using BLAST 2 Sequences, align the following sequences. Select blastp as
   ‘Program’.
       >K_transport
       VGALLLYLPISTTRPISFLDALFTATSAVTVTGLAVLDTYSDFTLFGKLVILFLIQVGGLGYMTLSTFFLVLLGRRIGLKER
       LILAESLEYPSMHGLIRFLKRVFSFVFITELTGAILLSIYFSLKGVEDPVFNGIFHSVSAFNNAGFSTFKNG

       >TRK system potassium uptake protein
       NDIQTKYALIVTAFISIIISIKDKVPIIDSLFTVVSAMTSTGFTTINVGNLSSLSLFLIIFLMLIGGGAGTTTGGVKIIRFL
       VILKALLYEIKEIIYPKSAVIHEHLDDMDLNYRIIREAFVVFFLYCLSSFLTALIFIALGYNPYDSIFDAVSF


       - Compare alignments with ‘Matrix’ BLOSUM62/BLOSUM80/
       /PAM30/PAM70. Any change when changing matrices?

       PAM (Percentage of Acceptable point Mutations per 108 years) matrices
       BLOSUM (BLOcks SUbstitution Matrix) matrices

B. Creating Multiple Sequence Alignments (MSA)
Objective: Perform multiple sequence alignments, calculate distance matrices, and
construct phylogenetic trees, to understand and interpret relationships between species.

In this example, we will create a multiple alignment of protein sequences that will be
imported into the alignment editor using different methods. Multiple protein sequence
alignment is a central tool to infer protein function, predict protein secondary structure,
and identify residues important for protein specificity.

Open the file ‘FT proteins for MEGA.doc’.
B1. Start MEGA4 by using Start\Programs\BioInformatics\MEGA4.
B2. In the MEGA4 window, go to Alignment|Alignment Explorer/CLUSTAL. Select
        ‘Create a new alignment’, and click on OK. Click on [NO] for protein sequence
        alignment.
B3. Sequences can be entered either from FASTA files (opening the concatenated
       FASTA sequences TXT file using MEGA) or by hand. We will enter the
       sequences by hand, one by one. In the Alignment Explorer window, go to
       Edit|Insert Blank Sequence or click on        , and repeat it to generate 8 blank
       sequences. Right-click on the blank sequence name and edit the sequence name
       for each protein sequence, as it is in the Word document ‘FT Proteins for MEGA’.
       Copy and paste each sequence.
B4. Go to Edit|Select All to select every site for all the protein sequences in the
      alignment.

B5. Go to Alignment|Align by ClustalW or click on           to align the selected protein
      sequences using the ClustalW algorithm.



                                                                                              4
B6. Save the current alignment by selecting the Data|Save Session. Save it as ‘FT.mas’.
       This will allow the current alignment to be restored for future editing. Also,
       export it (Data|Export Alignment|FASTA format) as both a FASTA file
       (‘FT.fas’) and a MEGA file (‘FT.meg’).


C. Generating a publishable MSA using BoxShade
C1. Using Word, open the previously created FASTA file (‘FT.fas’). Copy the FASTA
       sequences (including gaps). Past them in BOXShade:
       http://www.ch.embnet.org/software/BOX_form.html. In the ‘Output format’
       select RTF_new and in the ‘Input sequence format’ select other. Click on Run
       BOXSHADE. Click On ‘here is your output number 1’. The alignment will be
       open in a Word document.
D. Exploring the MSA and identifying patterns
D1. Back in MEGA4, exit the Alignment Explorer window by selecting the Data|Exit
      AlnExplorer. A dialog box will appear asking you if you would like to open the
      data file in MEGA; click on ‘Yes’.
D2. Observe different coloring schemes by clicking on: C: conserved residues (the same
      amino acid at a given site in all the aligned sequences), V: variable residues (at
      least 2 different amino acids at a given site), Pi: Parsimony informative (at least 2
      different amino acids at a given site and at least 2 of them occurring with a
      minimum frequency of 2), S: singletons (at least 2 different amino acids at a given
      site with at most 1 of them occurring multiple times).
          (When you have a coding DNA sequence you can translate it into a protein
          sequence by clicking on UUC->Phe. Clicking again you go back to the DNA
          sequence).
      -   Can you discover some groups by looking at the Pi characters?
      -   Move sequences to have OsFT2 close to TaFT2, and also TaFT, OsFTa, and
          OsFTb close to each other. Can you see patterns now?
D3. To see the format of a MEGA file, in the MEGA4 window, go to File|Export Data,
       and click on OK to take a look at it. Exit (File|Exit Editor) this window.
D4.




Mutations T                            V                                  L
TaFT2     Q                            D                               P




                                                                                          5
Which of the 3 mutations found in a TILLING screen of TaFT2 would you prioritize for
      characterizing a non-functional TaFT2 gene?
BLOSUM62 information for mutations: TQ= -1; VD=-3; LP=-3
BLOSUM62 information for changes at the mutation positions: TI= -1; VI=3; IL=2; EL=-2)
Maximize the conservation of the position and the negative impact of the mutation…

D5. Using T-COFFEE as a consistency based program
Copy the sequences below and open t-COFFEE in your web browser: http://tcoffee.vital-
it.ch/cgi-bin/Tcoffee/tcoffee_cgi/index.cgi. Use the Regular form of T-COFFEE. Paste
the sequences in the INPUT window and press submit. Click on the link for score_pdf
and save the file. (NOTE: Once the file is saved you may need to rename it so that it is a
.pdf file, or it may not open properly.)

>OsVIL1
MASSAGGDPPPPGLFAAALHACSGASALEEHIHADDSNTISDNTLEQLGFLDQESNDASVNTEKIQSSTPKCKSVEDIPIAPAAKRCKN
MDSKKLVPNSNNNSCLTGSQAPRKLPRKGDYPVQLRRNETFQDTKPPSTWICKNAACKAVLTADNTFCKRCSCCICHLFDDNKDPSLWL
VCSSETGDRDCCESSCHIECALQHQKVGCVDLGQSIQLDGNYCCAACGKVIGILGFWKRQLMVAKDARRVDILCSRIYLSHRLLDGTTR
FKEFHKIVEDAKAKLETEVGPLDGTSSKMARGIVGRLPVAADVQKLCSLAIDMADAWLKSNCKAETKQIDTLPAACRFRFEDITTSSLV
VVLKEAASSQYHAIKGYKLWYWNSREQPSTRVPAIFPKDQRRILVSNLQPCTEYAFRIISFTEYGDLGHSECKCFTKSVEIIHKNMEHG
AEGCSSTAKRDSKSRNGWSSGFQVHQLGKVLRKAWAEENGCPSEACKDEIEDSCCQSDSALHDKDQAAHVVSHELDLNESSVPDLNAEV
VMPTESFRNENICSPGKNGLRKSNGSSDSDICAEGLVGEAPAMESRSQSRKQTSDLEQETYLEQETGADDSTLLISPPKHFSRRLGQLD
DNYEYCVKVIRWLECSGHIEKDFRMKFLTWFSLRSTEQERRVVITFIRTLADDPSSLAGQLLDSFEEIVSSKKPRTGFCSKLWH*

>TmVIL1
MESTGGDPSGFAAAALHASSDVSEHEEIKPADDSNTISDYAQEPLNFFPEQESNDASVSTEKKESVVSKCKSVEEIPREATVKRCKNID
SKKLFSNNKNSPSLTGIQALRKPPRKGPHPIQLRESEMFQDKKPPSTWICKNAACKAVLTSENTFCKRCSCCICHLFDDNKDPSLWLVC
SSETGDTDCCESSCHVECALQRRKAGRIDLGQSMHLDGNYCCAACGKVIGILGFWKRQLAVAKDARRVDILCSRIYLSHRLLDGTTRFK
ELHQIVQDAKAKLETEVGPLDGSSKMARCIVGRLPVAADVQKLCSLAMEKVDDWLQSNSQAETKQIDTLPTACRFRFEDITASSLVIVL
KETASSQYHAIKGYKLWYWNSREPPSTGEPVIFPKDQRRILISNLQPCTEYAFRIISFVEDGELGHSESKCFTRSVEIMHKNIEHGAEG
CSSTAKRNVKRHNGRSSGFKVRQLGKVLRRAWEEDGFPSEFCKDEIEDSCDQSDSVILEKGQVAHVVSRKLDLNETSVPDLNAEVVMPT
ECLRNENAYSSGKNDLRKSNGCGDFATCTEGHVGEAPAMESRSQSRKQTSDLEQETCAEDGNLVIGSQRHFSRRLGELDNNYEYCVKTI
RWLECCGHIEKEFRMRFLTWFSLRSTEQERRVVLTFIRTLVDEPGSLAGQLLDSFEEIVASKRPRTGFCTKLWH*

>OsVIL2
MDPPYAGVPIDPAKCRLMSVDEKRELVRELSKRPESAPDKLQSWSRREIVEILCADLGRERKYTGLSKQRMLEYLFRVVTGKSSGGGVV
EHVQEKEPTPEPNTANHQSPAKRQRKSDNPSRLPIVASSPTTEIPRPASNARFCHNLACRATLNPEDKFCRRCSCCICFKYDDNKDPSL
WLFCSSDQPLQKDSCVFSCHLECALKDGRTGIMQSGQCKKLDGGYYCTRCRKQNDLLGSWKKQLVIAKDARRLDVLCHRIFLSHKILVS
TEKYLVLHEIVDTAMKKLEAEVGPISGVANMGRGIVSRLAVGAEVQKLCARAIETMESLFCGSPSNLQFQRSRMIPSNFVKFEAITQTS
VTVVLDLGPILAQDVTCFNVWHRVAATGSFSSSPTGIILAPLKTLVVTQLVPATSYIFKVVAFSNYKEFGSWEAKMKTSCQKEVDLKGL
MPGGSGLDQNNGSPKANSGGQSDPSSEGVDSNNNTAVYADLNKSPESDFEYCENPEILDSDKASHHPNEPTNNSQSMPMVVARVTEVSG
LEEAPGLSASALDEEPNSAVQTQLLRESSNSMEQNQRSEVPGSQDASNAPAGNEVVIVPPRYSGSIPPTAPRYMENGKDISGRSLKAKP
GDNILQNGSSKPEREPGNSSNKRTSGKCEEIGHKDGCPEASYEYCVKVVRWLECEGYIETNFRVKFLTWYSLRATPHDRKIVSVYVNTL
IDDPVSLSGQLADTFSEAIYSKRPPSVRSGFCMELWH*

>TmVIL2
MDPPYAGAIIEPAKCRLMSVDEKKDLVRELSKRPQTAPDKLQSWSRRDIVEILCADLGRERKYTGLSKQRMLDYLFRVVTGKSSGPVVH
VQEKEPTLDPNTSNHQYPAKRQRKSDNPSRLPIAVNNPQTAVVPVQINNVRSCRNIACRAILSMEDKFCRRCSCCICFKYDDNKDPTIW
LSCSSDHPMQKDSCGLSCHLECALKDGRTGILPSGQCKKLDGAYYCPNCRKQHDLLRSWKKQLMLAKEARRLDILCYRIFLGHKVLFST
EKYSVLHKFVDIAKQKLEAEVGSVAGHGSMGRGIVSRLTCGAEVQKLCAEALDVMQSKFPVESPTNSQFERSNMMPSSFIKFEPITPTS
ITVVFDLARCPYISQGVTGFKVWHQVDGTGFYSLNPTGTVHLMSKTFVVTALKPATCYMIKVTAFSNSSEFVPWEARVSTSSLKESDLK
GLAPGGAGLVDQNNRSPKTNSGGQSDRSSEGVDSNNNATVYTDLNKSPESDFEYCENPEILDSDKVPHHPNGPSNNLQNMQIVAARVPE
VTELEEAPGLSASALDEEPNSTVQAALLRESSNSMEQNQRSEVPISQDASNATAGVELALVPRFVGSMPPTAPRVMETGKETGGRSFNT
KPSDNIFQNGSSKPDREPGNSSNKRSGKFEDAGHKDGCPEATYEYCVRVVRWLETEGYIETNFRVKFLTWYSLRATPHDRKIVSVYVDT
LINDPASLCGQLTDTFSEAIYSKKPPSVPSGFCMNLWH*

Note: NCBI multiple alignment tool for proteins is COBALT: it does progressive multiple
alignment of protein sequences. The alignment is aided by a collection of pairwise constraints
derived from conserved domain database, protein motif database, and local sequence similarity
using RPS-BLAST, BLASTP, and PHI-BLAST, respectively. Computation time is reduced by
forming clusters of sequences that share a large number of common words and finding
conserved domains and motif matches for only one sequence per cluster.


                                                                                                 6
D6. Creating a graphical representation of amino acid conservation.
A FASTA file of the first 50 amino acids of the FT protein alignment has been saved in
the 10_Lab3 folder. Open the FASTA file, ‘FTclipped.fas’, using Microsoft Word.
Copy the FASTA alignment and paste it in the Multiple Sequence Alignment window of
       WebLogo: http://weblogo.berkeley.edu/logo.cgi. Click Create Logo.




E. Calculating a Distance Matrix
E1. In the MEGA4 window, go to Distances|Compute Pairwise. In the ‘Analysis
        Preferences’ window, change ‘Model’ to Amino Acid|No. of differences (leave
        the default parameters in the other options). Click on Compute.
E2. See the Pairwise Distances matrix.
   -   Which sequences are the closest ones?
   -   Which sequences are the most distant ones?
E3. To see the matrix in a MEGA file and save it, go
       to File|Export/Print Distances, and change
       the ‘Output Format’ from ‘Publication’ to
       ‘MEGA’. Click on Print/Save Matrix.
E4. After you have inspected the matrix, go to File|Quit Viewer to close the Pairwise
       Distances matrix.


F. Drawing a Phylogenetic Tree
F1. In the MEGA4 window, go to Phylogeny|Construct Phylogeny|Neighbor-Joining
       (NJ). In the ‘Analysis Preferences’ window, in the ‘Options Summary’ tab,
       change ‘Model’ to Amino Acid|No. of differences. (leave the default parameters
       in the other options). Click on Compute.
F2. See the tree in the Tree Explorer window.
F3. To select a branch, left-click on it. If you right-click on a branch, you will find
      several options to perform different operations on the ‘Selected subtree’. To edit
      the accession labels, double-click on them. Change the branch style by selecting
      the View|Tree/Branch Style.




                                                                                           7
F4. To save the tree to the clipboard and then be able to save it in a Word document, go
       to Image|Copy to clipboard. Open a Word document and paste this tree. Exit the
       Tree Explorer window (File|Exit Tree Explorer), without saving.
-      Use Phylogeny|Contruct Phylogeny to produce minimum evolution, maximum
       parsimony and UPGMA trees. Copy and paste each of them into the same Word
       document to compare them. Are the results consistent?


       NJ                                                            OsFTa
                                                                      TaFT
                                                                        OsFTb
                                                                       OsFT2
                                                                               TaFT2
                                                                       AtFT
                                                                       AtTSF
                                                                               AtTFL1

       UPGMA                       10
                                                                                   OsFTa
                                                                                   TaFT
                                                                                   OsFTb
                                                                                   OsFT2
                                                                                   TaFT2
                                                                                   AtFT
                                                                                   AtTSF
                                                                                   AtTFL1


                                   30           20            10               0


       Max                                                                           AtFT
       Parsimony                                                                     AtTSF
                                                                                     AtTFL1
                                                                                     TaFT
                                                                                     OsFTa
                                                                                     OsFTb
                                                                                     OsFT2
                                                                                     TaFT2




                                                                                              8
       Min                                                               OsFTa
       Evolution                                                         TaFT
                                                                           OsFTb
                                                                         OsFT2
                                                                                 TaFT2
                                                                         AtFT
                                                                         AtTSF
                                                                                 AtTFL1


                                    10




G. Evaluating a Phylogenetic Tree
G1. In the MEGA4 window, go to Phylogeny|Construct Phylogeny|Neighbor-Joining
        (NJ). In the ‘Analysis Preferences’ window, in the ‘Test of Phylogeny’ tab, select
        ‘Bootstrap’ with 1,000 replications. Click on Compute.
G2. See the tree and the bootstrap values in the Tree Explorer window.
   -   What is the confidence of the OsFTa-TaFT branch?
G3. Go to Image|Copy to clipboard and paste the tree into your Word document. Exit
      the Tree Explorer window (File|Exit Tree Explorer), without saving.




H. Within MEGA Alignment Explorer we can retrieve sequences directly from
GenBank
We have discovered a MADS box protein from barley (GenBank # CAB97352) and we
want to determine the closest protein in among the following three Arabidopsis proteins:
AP1= CAA78909; AGL2= AAA32732; AGL6= AAA79328).
H1. In the MEGA4 window, go to Alignment|Query databanks.
H2. In the NCBI Entrez site, select Protein database, enter the first GenBank number
        CAB97352 into the search box, and click on Go. When the search result is
        displayed, open it and then click on ‘Add to Alignment’.



                                                                                           9
 H3. Repeat step G2. for the three Arabidopsis sequences.
 H4. Align the protein sequence using ClustalW as before, save the alignment as
        ‘MADS.mas’, exit and open the file in MEGA.
 H5. Perform a Neighbor-Joining (NJ) analysis. Copy and paste the phylogenetic tree
        into your Word document.
     -   Which Arabidopsis protein is the closest one to the MADS box protein from
         barley?




 I. Viewing the 3D structure of a protein
 I1. Cn3D is an application that allows you to view 3-dimensional structures of proteins.
        Go to protein blast (blastp).
         Copy and paste AtFT protein sequence and click on BLAST.
 I2. Once your results are completely displayed, go to Show Conserved Domains.
     -   What is the name of the conserved domain?




                         Click on it to find more information about the conserved domain.
                            - What biological functions have been attributed to this
                         conserved domain?
                         H3. Click on Structure to go to Entrez, Structure database. In
                         the Structure database, insert the name of the conserved domain
                         you found and click on Go. Click on the link displayed as your
                         results. In the Structure Summary window, click on Structure
                         View in Cn3D. Open the file with Cn3D. Cn3D tutorial:
                         http://www.ncbi.nlm.nih.gov/Structure/CN3D/cn3dtut.shtml .


I4. Go to View|Animation|Spin for a complete view of the 3D structure of the conserved
    domain. You can change the Style in which you want to see the 3D structure.


                                                                                        10
The default display presented in the figure for single structures is a combination of
   Style/Rendering Shortcuts: Worms and Style/Coloring Shortcuts: Secondary
   Structure, which show a worm backbone, no side chains, and solid objects - arrows
   and cylinders - to represent strands and helices. The colors are green for helices,
   orange for strands, and blue for coils. Arrows point in the N-to-C direction.
I5. In the Sequence/Alignment Viewer, you can see where in the 3D structure the selected
    amino acids are located, by simply selecting them with your mouse. The 3D structure
    will be highlighted in the position where the selected amino acids are located.
 Align a query protein to a similar sequence from a 3D structure and interactively view
 sequence/structure relationships

  Even if a 3D structure for your protein of interest has not yet been resolved, it is possible to
  align your query protein to a similar sequence from a 3D structure.

     1. Open the Entrez Protein (http://www.ncbi.nlm.nih.gov/protein) search page

     2. Retrieve your sequence record of interest, for example wheat FT AAW23034

     3. In the Links menu in the right select Related Structure (Summary) (at the bottom of
        the right list). This will retrieve a list of protein sequences that are present in 3D structure
        records and that were found by CBLAST (compares a query protein against all protein
        sequences from resolved 3D structures).

     4. To view a sequence alignment of the query and a hit of interest (2IQY_A), click on the
        pink bar that represents the alignment.




     5. On the sequence alignment display, press the View Structure and Alignment in Cn3D
        button to save the file and then open with Cn3D

     6. Once the Cn3D display is open, you can click on any amino acids from the retrieved
        structure, in either the 3D structure or the sequence alignment window, to highlight their
        location in both views and examine the sequence/structure relationship. The Cn3D
        Tutorial provides more information about using the program, and the third comment
        under additional notes, below, provides step-by-step instructions on how to generate the
        specific view shown in the illustration on this page.




                                                                                                 11
J. From Multiple Sequence Alignment to Multiple Sequence Assembly
J.1. Using MEGA4, perform a new ClustalW alignment with the 8 exported sequences
       used in 10_Lab1 (simply select them all from the Word document called
       ‘10_Lab1 DNA for MEGA’, copy them (Ctrl C) and paste them (Ctrl V) in the
       MEGA4 Alignment Explorer window).
   -   Could you get a good alignment of the sequences? Why?
   -   How would you find the alignment between the overlapping regions that are
       present in these sequences?




                                                                                   12

								
To top