CHARACTERIZATION OF A FOLDING INTERMEDIATE FROM HIV-1 RIBONUCLEASE-H

The RNase H domain from HIV-1 (HIV RNase H) encodes an essential retro viral activity. Refolding of the isolated HIV RNase H domain shows a k inetic intermediate detectable by stopped-flow far UV circular dichroi sm and pulse-labeling H/D exchange. In this intermediate, strands 1, 4 , and 5 as well as helices A and D appear to be structured. Compared t o its homolog from Escherichia coli, the rate Limiting step in refoldi ng of HIV RNase H appears closer to the native state. We have modeled this kinetic intermediate using a C-terminal deletion fragment lacking helix E. Like the kinetic intermediate, this variant folds rapidly an d shows a decrease in stability. We propose that inhibition of the doc king of helix E to this folding intermediate may present a novel strat egy for anti HIV-1 therapy.