THREE DIMENSIONAL STRUCTURE OF A PLANT CARDOON ASPARTIC PROTEINASE. C. Frazco, I. Bento, R. Coelho, J. Costa, ITQB, Apt. 127, 2780-Oeiras, Portugal, C. Faro, P. Vermssimo, E. Pires, Dep. Bioqummica, Fac. Cijncias e Tecnologia, Univ. Coimbra, 3000 Coimbra, Portugal, J. Cooper, Lab. Molecular Biology, Dept. Crystallography, Birkbeck College, Malet Street, London WC1E 7HX, UK, Z. Dauter, K. Wilson, EMBL, c/o DESY, Notkestrasse 85, 22603 Hamburg, Germany, and M. A. Carrondo, ITQB and IST, Apt. 127, 2780-Oeiras, Portugal

Although aspartic proteinases are widely dispersed in the vegetal kingdom, their structures and biological functions are less well characterized than those of animal, microbial and viral aspartic proteinases. A native, glycosylated aspartic proteinase, cardosine A, isolated from the cardoon flower (1), which is traditionally used in Portugal for cheese making, was crystallized and its structure solved by the molecular replacement method, using the structure of human cathepsin D (2) as a model. Cardosine A is composed of two polypeptide chains and is expressed with the ca. 100 residues insertion, also found in other vegetal aspartic proteinases. However, its mature native form does not show the insertion anymore.

Crystals were obtained in space goup C₂, a=119.0, b=88.1, c=82.3 E, b=104.4 , with two molecules in the asymmetric unit. Syncrotron diffraction data to 2.9 E resolution were collected at the EMBL outsation, Hamburg. Refinement is in progress, with an actual of R=29.4% and Rfree=35.0%.

(1) P. Vermssimo et al. (1996) Eur. J. Biochem., in press.

(2) E.T. Baldwin et al. (1993) Proc. Nat. Acad. Sci. USA 90, 6796-6800.