Murder at the airport - Part 3

Exercise 5:

Let's have a look at the first hit, casa1_bovin. Click on the coloured bar, then on the two-coloured bar. Analyse the results.

Alignment of casa1_bovin, click here for a larger picture

You now see a so-called alignment of the two amino acid sequences. Q (query) is the sequence that you have entered, in this case suspect1. S is the protein sequence from the database that looks most like suspect1, in this case casa1_bovin. The line between these two sequences contains the letters of all amino acids that are identical in Q and S. If not all amino acids are identical, you will see gaps (you can take a closer look later). You may have noticed that a small part of the query sequence is crossed out. This part was not used in your BLAST search because of a low-complexity filter: it removes parts of your query that are likely to give irrelevant hits.

As you can see, the sequence of suspect1 is 100% identical to the sequence of casa1_bovin, the alpha-S1-casein protein (all 199 amino acids are identical). Thus, you have successfully identified one of the four proteins. Click on casa1_bovin to go to the database record and see all known data about this protein, in order to find out if this protein could be involved in the death of the tourist.

Information about casa1_bovin, click for a larger picture

Exercise 6:

The database record for casa1_bovin contains everything you need to know to answer the five questions about your protein:

  1. Which protein is it?
  2. From which organism does it originate?
  3. What is the function of this protein?
  4. Is this protein "guilty"? Could it be responsible for the death of the tourist? Why (not)?
  5. Does the protein have any other remarkable features?

If you do not know where to look, use the hints below:

So, what is your conclusion? Is protein suspect1 involved in the death of the tourist, yes or no?

Exercise 7: Now analyse the other 3 suspicious proteins by yourself!

Run a BLAST search with the sequences of the other 3 proteins and write down your results.

What is your final conclusion about the murder? How did the victim die? Answers

A closer look...

Well done, you have now established how the victim died, the police will have to figure out the rest. In the process you have learned a lot about a specific part of bioinformatics: analysing protein sequences using bioinformatics tools and databases. This brings us to the end of our murder investigation.

If you have some time left and if you are interested, you can see some more of the many exciting possibilities of bioinformatics. In this additional part, you will find a few exercises which further explore protein sequences, important amino acids, homology between similar organisms, etc.

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