Residue determinants and sequence analysis of cold-adapted trypsins |
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Authors: | H-K Schrøder Leiros Nils Peder Willassen A O Smalås |
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Institution: | Protein Crystallography Group, Department of Chemistry, Faculty of Science, University of Troms?, N-9037 Troms?, Norway Tel. +47 77 64 40 70; Fax +47 77 64 47 65 e-mail: arne.smalas@chem.uit.no, NO Institute of Medical Biology, Faculty of Medicine, University of Troms?, N-9037 Troms?, Norway, NO
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Abstract: | The digestive enzyme trypsin is among the most extensively studied proteins, and its structure has been reported from a large
number of organisms. This article focuses on the trypsins from vertebrates adapted to life at low temperatures. Cold-adapted
organisms seem to have compensated for the reduced reaction rates at low temperatures by evolving more active and less temperature-stable
enzymes. We have analyzed 27 trypsin sequences from a variety of organisms to find unique attributes for the cold-adapted
trypsins, comparing trypsins from salmon, Antarctic fish, cod, and pufferfish to other vertebrate trypsins. Both the "cold"
and the "warm" active trypsins have about 50 amino acids that are unique and conserved within each class. The main unique
features of the cold-adapted trypsins attributable to low-temperature adaptation seem to be (1) reduced hydrophobicity and
packing density of the core, mainly because of a lower (Ile + Leu)/(Ile + Leu + Val) ratio, (2) reduced stability of the C-terminal,
(3) lack of one warm trypsin conserved proline residue and one proline tyrosine stacking, (4) difference in charge and flexibility
of loops extending the binding pocket, and (5) different conformation of the "autolysis" loop that is likely to be involved
in substrate binding.
Received: January 14, 1999 / Accepted: March 31, 1999 |
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Keywords: | Cold adaptation Psychrophilicity Residue determinants Sequence comparison Trypsin |
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