Critical evaluation of comparative model building of Streptomyces griseus trypsin.

The X-ray crystal structure of Streptomyces griseus trypsin has been solved and refined at 1.7-A resolution. The structure of this protein had been predicted in two models on the basis of its expected homology to structures of bovine trypsin and other pancreatic serine proteases [Jurásek, L., Olafson, R.W., Johnson, P., & Smillie, L.B. (1976) Miami Winter Symp. 11, 93-123; Greer, J. (1981) J. Mol. Biol. 153, 1027-1042]. An evaluation of these models in light of the known structure demonstrates the effect of several sources of error on such comparative model building. The objective of comparative model building is often to explain substrate specificity, or to suggest potential highly specific drugs. The unique parts of modeled proteins that are most important for such purposes are, however, the most poorly determined by the model-building procedure.