W0140

Crystal structure of prophytepsin, a zymogen of barley-grain aspartic proteinase. A.Zdanov, J. Kervinen, D. Waugh, A.Wlodawer, ABL-Basic Research Program, G. Tobin, G. Li, LCMG, SAIC, NCI-FCRDC, P.O. Box B, Frederick, MD 21702 USA

Phytepsin belongs to a family of aspartic proteinases which includes pepsin, chymosin, cathepsin D and HIV-1 proteinase. Amino acid sequence of phytepsin is similar to other aspartic proteinases although this similarity is divided between two regions, separated by unique plant-specific domain of 104 residues.

Recombinant preprophytepsin was expressed in baculovirus-infected insect cell system and proform was purified from cell media. Now we have obtained monoclinic crystals of prophytepsin. Unit cell parameters are a=66.0Å, b=160.9Å, c=81.4Å, =109.6^o, space group is P2₁. There are two molecules in the asymmetric unit. We collected diffraction data at 2.3Å resolution at synchrotron facilities in CHESS. Putative molecular replacement solution have been obtained by using the coordinates of cathepsin D and pepsinogen as a starting model. Refinement of the structure of prophytepsin at high resolution is in progress.