BINDING OF RNA TEMPLATE TO A COMPLEX OF HIV-1 REVERSE TRANSCRIPTASE PRIMER/TEMPLATE/

HIV-1 reverse transcriptase (RT) catalyzes the synthesis of DNA from D NA or RNA templates, During this process, it must transfer its primer from one template to another RNA or DNA template, Binary complexes mad e of RT and a primer/template bind an additional single-stranded RNA m olecule of the same nucleotide sequence as that of the DNA or RNA temp late, The additional RNA strand leads to a 10-fold decrease of the off -rate constant, k(off), of RT from a primer/DNA template, in a binary complex of RT and a primer/template, the primer can be cross-linked to both the p66 and p51 subunits, Depending on the location of the photo reactive group in the primer, the distribution of the cross-linked pri mers between subunits is dependent on the nature of the template and o f the additional single-stranded molecule, Greater cross-linking of th e primer to p51 occurs with DNA templates, whereas cross-linking to p6 6 predominates with RNA templates. Excess single-stranded DNA shifts t he distribution of cross-linking from p66 to p51 with RNA templates, a nd excess single-stranded RNA shifts the cross-linking from p51 to p66 with DNA templates, RT thus uses two primer/template binding modes de pending on the nature of the template.