Murder at the airport

Exercise 1:

Start MRS.

The opening screen looks like this:

Exercise 2:

Click BLAST in the menu to start the program

Below, you see an example containing the amino acid sequence of the first suspect. The first line should always start with a >, followed by the name of the protein (this is the so-called FastA format). Here we chose the name suspect1.

Exercise 3:

This is the amino acid sequence of the first protein: (already in FASTA format)

>suspect1
RPKHPIKHQG LPQEVLNENL LRFFVAPFPE VFGKEKVNEL SKDIGSESTE DQAMEDIKQM
EAESISSSEE IVPNSVEQKH IQKEDVPSER YLGYLEQLLR LKKYKVPQLE IVPNSAEERL
HSMKEGIHAQ QKEPMIGVNQ ELAYFYPELF RQFYQLDAYP SGAWYYVPLG TQYTDAPSFS
DIPNPIGSEN SEKTTMPLW

  • Copy the sequence of suspect1 into the BLAST window
  • Make sure that the Filter sequence (low complexity) box is cleared
  • Click on Run BLAST (top right of the window)

You are now forwarded to the next screen, showing running while BLAST is busy. If many people are using BLAST simultaneously, this may take some time. Do not forget that you are working with a database containing hundreds of thousands of protein sequences.

When the search is completed, a table showing the results appears, which looks like the one given here (the numbers may vary because of SwissProt updates) :

This output means that 101 hits have been found in the SwissProt database. In other words, 101 proteins have an amino acid sequence similar to suspect1. The number under e-Value shows how good the best result is. If this number is small (which is the case here, since it is 6.59 x 10-113), the result is reliable.

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