MODELING, SYNTHESIS AND BIOLOGICAL-ACTIVITY OF A BLV PROTEINASE, MADEOF (ONLY) 116 AMINO-ACIDS

Bovine leukaemia virus (BLV) is the aetiological agent of Leukosis enz ootica bovis [Viral Oncology (1980), G. Klein (Ed.) Raven Press, New Y ork, pp. 231-238], a widely spread disease in cattle. BLV is reported as the animal model of human T-cell leukaemia virus (HLTV) which is th e causative agent of adult T-cell leukaemia and tropical spastic parap aresis. Like the viruses themselves, the two retroviral proteinases (P R) are very closely related [Virology 142 (1985) 357-377]. BLV and HTL V-1 PR are reported as putative proteins made of 126 [J. Virol. 57 (19 86) 826-832] and 125 [FEBS Lett. 293 (1991) 106-110] amino acids, resp ectively (long sequences), belonging to the aspartyl proteinase family [Nature 329 (1987) 351-354], with the aid of molecular modelling, we show that BLV and HLTV-1 proteinases made of only 116 and 115 amino ac ids, respectively (short sequences), display three-dimensional structu res similar to that observed for other retroviral aspartyl proteinases . The models are based on three-dimensional structures of the Rous sar coma virus (RSV PR) and the human immunodeficiency virus (HIV-1 PR). W e used solid phase peptide synthesis to produce the putative proteolyt ic enzyme of BLV (1 16 amino acids). In this study, we show that the f olded synthetic protease accurately hydrolyzes a decapeptide correspon ding to the sequence of the Matrice-Capside (MA/CA) cleavage site of t he gag polyprotein. In addition, the proteolytic activity is inhibited by a statine ((4S,3S)-4-amino-3-hydroxyl-6-methylheptanoic acid) cont aining an analogous sequence.