1.8 ANGSTROM STRUCTURE OF HYPODERMA-LINEATUM COLLAGENASE - A MEMBER OF THE SERINE PROTEINASE FAMILY

Collagenase from the fly larvae Hypoderma lineatum cleaves triple-heli cal collagen in a single region. It was crystallized at neutral pH in the absence of inhibitor and 1.8 Angstrom data were collected using sy nchrotron radiation and a Mark II prototype detector. The structure wa s solved by combining multiple isomorphous replacement methods and rot ation translation function in real space. Refinement between 7 and 1.8 Angstrom using the program X-PLOR led to a final R factor of 16.9%. T he overall fold is similar to that of other trypsin-like enzymes but t he structure differs mainly by the presence of a beta-sheet at positio n 31-44. The two embedded molecules of the asymmetric unit are related by a pseudo twofold axis. The beta-sheet 31-44 of one molecule is inv olved in hydrogen bonds with binding-pocket residues of the other mole cule. It thus completely prevents access to the active site. The speci ficity of this enzyme probably results from the position of Phe192 and Tyr99 at the entrance of the active site.