Crystallographic and kinetic investigations of the covalent complex formed by a specific tetrapeptide aldehyde and the serine protease from Streptomyces griseus.

X-ray crystallographic data show that a specific tetrapeptide aldehyde inhibitor (N-acetylprolylalanylprolylphenylalaninal) forms a stable, covalent, tetrahedral addition complex with the serine protease, SGPA, from Streptomyces griseus. Earlier proposals, based on kinetic measurements, for the covalent nature of such linkages are confirmed, and the difference electron density map of this aldehyde inhibitor indicates that a major conformational change of the histidyl-57 side chain occurs on inhibitor binding.