RESUMEN

The biologically active form of HIV-1 reverse transcriptase (RT) is the p66/p51 heterodimer. The process of maturation of the heterodimer from precursor proteins is poorly understood. Previous studies indicated that association of p66 and p51 is very slow. Three techniques, a pre-steady-state activity assay, intrinsic tryptophan fluorescence, and a FRET assay, were used to monitor the dimerization kinetics of RT. Kinetic experiments were conducted with purified p66 and p51 proteins in aqueous buffer. All three techniques gave essentially the same results. The dissociation kinetics of p66/p51 were first-order with rate constants (k(diss)) of approximately 4 x 10(-6) s(-1) (t(1/2) = 48 h). The association kinetics of p66 and p51 were concentration-dependent with second-order rate constants (k(ass)) of approximately 1.7 M(-1) s(-1) for the simple bimolecular association reaction. The implications of slow dimerization of p66/p51 for the maturation process are discussed. A reaction-controlled model invoking conformational selection is proposed to explain the slow protein-protein association kinetics.

Asunto(s)

Transcriptasa Inversa del VIH/química , Sustitución de Aminoácidos , Secuencia de Bases , Cartilla de ADN/genética , Dimerización , Transferencia Resonante de Energía de Fluorescencia , Transcriptasa Inversa del VIH/genética , Transcriptasa Inversa del VIH/metabolismo , VIH-1/enzimología , VIH-1/genética , Cinética , Modelos Moleculares , Mutagénesis Sitio-Dirigida , Estructura Cuaternaria de Proteína , Subunidades de Proteína , Proteínas Recombinantes/química , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Espectrometría de Fluorescencia , Termodinámica , Triptófano/química