Sequence searches and multiple sequence alignments (Phenylketonuria)

Summary of the task

In this task we compare the protein sequence of interest, in this case the phenylalanine hydroxylase (PAH), to other protein sequences. Therefore both sequence searches and multiple sequence alignments were done using the big80 database meaning a database that contains subsets of swissprot and pdb, where the entries have a sequence similarity of 80% or less. Furthermore searches against a pdb database were done. For sequence searches the programs BLAST, PSIBLAST and HHblits are used. Their results were taken for the creation of multiple sequence alignments (MSA) using he methods ClustalW, Muscle and TCoffee.

Sequence searches

The following invocations were used for Blast, PSI-Blast and HHBlits:

BLAST (Basic Local Alignment Search Tool)

nohup blastall -p blastp -d /mnt/project/rost_db/data/big/big_80 -i /mnt/home/student/worfk
/Masterpractical/Task2/PAH.fasta -o /mnt/home/student/worfk/Masterpractical/Task2/Blast/PAH
_Blast_big_80.out -v 2000 -b 2000 &

PSI-BLAST (Position-Specific Iterated BLAST)

For PSI-Blast (PSI-BLAST Tutorial) more than one vocation was performed. First two iterations were done with an E-value cutoff of 0.002 and then again with cutoff 10E-10. The same for ten iterations. An example vocation would be:

blastpgp -i /mnt/home/student/worfk/Masterpractical/Task2/PAH.fasta -d /mnt/project/rost_db
/data/big/big_80 -j 2 -h 0.002 -v 1000 -b 1000 -o psi_blast_big_80_2_2.out -C big_80_check_
2_2.chk -Q big_80_matrix_2_2.pssm

HHblits

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To perform all programms at once, one could use the Perl-script from Maria, like shown here:

perl /mnt/home/student/kalemanovm/master_practical/Assignment2_Alignments/scripts/task1/run.pl ...

Comparison of the results

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Multiple sequence alignments

ClustalW

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Muscle

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T-Coffee

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