Total chemical synthesis of human T-cell leukemia virus type 1 (HTLV-1) protease via native chemical ligation Reexamination of the functional effect of C-terminal truncation

• Published in: Biopolymers Vol. 94; no. 4; pp. 487 - 494
• Main Authors: Li, Changqing, Li, Xiangqun, Lu, Wuyuan
• Format: Journal Article
• Language: English
• Published: 01.01.2010
• ISSN: 0006-3525; 1097-0282
• DOI: 10.1002/bip.21375

Human T-cell leukemia virus 1 (HTLV-1) protease - a member of the aspartic acid protease family plays critical roles in the pathogenesis of the virus and is an attractive viral target for therapeutic intervention. HTLV-1 protease consists of 125 amino acid residues and functions as a homodimer stabilized in part by a four-stranded β-sheet comprising the N- and C-termini. Compared with many other viral proteases such as HIV-1 protease, HTLV-1 protease is elongated by an extra 10 amino acid residue “tail” at the C-terminus. The structural and functional role of the extra C-terminal residues in the catalysis of HTLV-1 protease has been a subject of debate for years. Using the native chemical ligation technique pioneered by Kent and colleagues, we chemically synthesized a full-length HTLV protease and a C-terminally truncated form encompassing residues 1–116. Enzyme kinetic analysis using three different peptide substrates indicated that truncation of the C-terminal tail lowered the turnover number of the viral enzyme by a factor of 2 and its catalytic efficiency by roughly tenfold. Our findings differ from the two extreme views that the C-terminal tail of HTLV-1 protease is either fully dispensable or totally required for enzyme dimerization and/or catalysis.