THE 80S LOOP (RESIDUES 78 TO 85) IS IMPORTANT FOR THE DIFFERENTIAL ACTIVITY OF RETROVIRAL PROTEASES

The abundance of structural data available for retroviral proteases af fords a unique opportunity to investigate structure activity relations hips. Our approach attempts to genetically engineer an HIV (human immu nodeficiency virus)-1 protease that is functionally equivalent to the HIV-2 and the SIV (simian immunodeficiency virus) enzymes and converse ly to engineer an HIV-2 protease that is functionally equivalent to th e HIV-1 enzyme. For this purpose, the HIV-2 and SIV proteases were clo ned and characterized in an Escherichia coli (E. coli) assay system al ong with 33 engineered HIV-1 and HIV-2 enzymes. The results of these e xperiments show that a relatively large S-1 or S-1' subsite volume, wh ich is likely determined by the conformation of the 80's loop (residue s 78 to 85), is necessary to fully accommodate the HIV-1 protease spec ificity site AETFYCDG (the asterisk indicates the location scissile b ond) during productive binding. (C) 1997 Academic Press Limited.