The Human Immunodefficiency Virus type 1

protease (HIV-1 PR) plays a critical role in the viral replication process by its involvement in the hydrolysis of the viral protein precursors [1, 2]. HIV-1 PR, a homodimer of known crystal structure with 99 aminoacids per chain, is included in the eukariotic aspartic protease family [3-5]. The β-sheet configurations, which include the triplet active site Asp 25/125-Thr 26/126-Gly 27/127 are present in the major part of the enzyme (aminoacids 1-85/101-185), whereas the α-helix domain covers the aminoacids 86-99 [3-6] (Fig. 1). Comparative study of some energetic and steric parameters of the wild type and mutants HIV-1 protease: a way to explain the viral resistanc