Source and target enzyme signature in serine protease inhibitor active site sequences |
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Authors: | Balaji Prakash M R N Murthy |
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Institution: | (1) Molecular Biophysics Unit, Indian Institute of Science, 560012 Bangalore, India |
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Abstract: | Amino acid sequences of proteinaceous proteinase inhibitors have been extensively analysed for deriving information regarding
the molecular evolution and functional relationship of these proteins. These sequences have been grouped into several well
defined families. It was found that the phylogeny constructed with the sequences corresponding to the exposed loop responsible
for inhibition has several branches that resemble those obtained from comparisons using the entire sequence. The major branches
of the unrooted tree corresponded to the families to which the inhibitors belonged. Further branching is related to the enzyme
specificity of the inhibitor. Examination of the active site loop sequences of trypsin inhibitors revealed that here are strong
preferences for specific amino acids at different positions of the loop. These preferences are inhibitor class specific. Inhibitors
active against more than one enzyme occur within a class and confirm to class specific sequence in their loops. Hence, only
a few positions in the loop seem to determine the specificity. The ability to inhibit the same enzyme by inhibitors that belong
to different classes appears to be a result of convergent evolution. |
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Keywords: | Protease inhibitors active site sequence signature evolution convergence |
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