The connection domain is implicated in metalloporphyrin binding and inhibition of HIV reverse transcriptase

We have shown that heme and zinc protoporphyrin inhibit both human immunode ficiency virus type 1 (HIV-1) and type 2 (HIV-2) reverse transcriptases (RT s) and, in combination with other nucleoside and non-nucleoside inhibitors, exert an additive effect on HIV-1 RT inhibition. Screening of a phage pept ide library against heme resulted in the isolation of a peptide with sequen ce similarity to sequence 398-407 from the connection subdomain of both HIV -1 and HIV-2 RTs, suggesting that this highly conserved region of HIV RTs c orresponds to the binding site for metalloporphyrins and a new site for inh ibition of enzyme activity Inclusion of a synthetic peptide corresponding t o the exact sequence 398-407 of HIV-1 RT in RT inhibition assays had a prot ective effect on metalloporphyrin inhibition, as it was able to reverse the inhibitory effect of both metalloporphyrins on HIV-1 RT activity. Furtherm ore, intrinsic fluorescence assays indicated that these metalloporphyrins b ind to synthetic peptide 398-407 as well as to intact dimeric HIV-1 RT. The identification of this novel inhibition site will help to expand our under standing of the rode of action of metalloporphyrins in RT inhibition and wi ll assist in the design and development of more potent metalloporphyrin RT inhibitors for the management of HIV infection.