title: Catalytic efficiency and vitality of HIV-1 proteases from African viral subtypes.
abstract: The vast majority of HIV-1 infections in Africa are caused by the A and C viral subtypes rather than the B subtype prevalent in the United States and Western Europe. Genomic differences between subtypes give rise to sequence variations in the encoded proteins, including the HIV-1 protease. Because some amino acid polymorphisms occur at sites that have been associated with drug resistance in the B subtype, it is important to assess the effectiveness of protease inhibitors that have been developed against different subtypes. Here we report the enzymatic characterization of HIV-1 proteases with sequences found in drug-naive Ugandan adults. The A protease used in these studies differs in seven positions (I13V/E35D/M36I/R41K/R57K/H69K/L89M) in relation to the consensus B subtype protease. Another protease containing a subset of these amino acid polymorphisms (M36I/R41K/H69K/L89M), which are found in subtype C and other HIV subtypes, also was studied. Both proteases were found to have similar catalytic constants, k(cat), as the B subtype. The C subtype protease displayed lower K(m) values against two different substrates resulting in a higher (2.4-fold) catalytic efficiency than the B subtype protease. Indinavir, ritonavir, saquinavir, and nelfinavir inhibit the A and C subtype proteases with 2.5-7-fold and 2-4.5-fold weaker K(i)s than the B subtype. When all factors are taken into consideration it is found that the C subtype protease has the highest vitality (4-11 higher than the B subtype) whereas the A subtype protease exhibits values ranging between 1.5 and 5. These results point to a higher biochemical fitness of the A and C proteases in the presence of existing inhibitors.
authors.affiliation: Department of Biology, The Johns Hopkins University, Baltimore, MD 21218, USA.
authors.forename: A
authors.initials: A
authors.lastname: Velazquez-Campoy
authors.forename: M J
authors.initials: MJ
authors.lastname: Todd
authors.forename: S
authors.initials: S
authors.lastname: Vega
authors.forename: E
authors.initials: E
authors.lastname: Freire
mesh_terms: D000328:Adult; D000595:Amino Acid Sequence; D002384:Catalysis; D015658:HIV Infections / Q000821:virology*; D016333:HIV Protease / Q000737:chemistry / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D017320:HIV Protease Inhibitors / Q000494:pharmacology; D015497:HIV-1 / Q000201:enzymology* / Q000235:genetics / Q000302:isolation & purification; D006801:Humans; D019469:Indinavir / Q000494:pharmacology; D008969:Molecular Sequence Data; D019888:Nelfinavir / Q000494:pharmacology; D017433:Protein Structure, Secondary; D019438:Ritonavir / Q000494:pharmacology; D019258:Saquinavir / Q000494:pharmacology; D014454:Uganda
chemical_list: D017320:HIV Protease Inhibitors; D019469:Indinavir; D016333:HIV Protease; D019888:Nelfinavir; D019258:Saquinavir; D019438:Ritonavir