Body's natural anti-HIV enzyme is examined

LOS ANGELES, -- U.S. medical scientists say they've deter- mined the atomic structure of a key enzyme involved in in- hibiting the human immunodeficiency virus. The researchers, led by Professor Xiaojiang Chen of the University of South- ern California, said the enzyme APOBEC-3G -- present in every human cell -- is capable of stopping HIV at the first step of replication, when the retrovirus transcribes its RNA into viral DNA. The reason APOBEC-3G works so well, but peo- ple still develop AIDS, is because the HIV virus has evolved to encode the protein Vif, which blocks APOBEC-3G. But Chen said his group's research offers important clues on where Vif binds to APOBEC-3G. Those findings, he said, could be used to design drugs that would prevent Vif from binding, allowing APOBEC-3G to do its job. That, he added, would un- lock humans' innate ability to fight HIV. The study that included Lauren Holden, Courtney Prochnow, Y. Paul Chang, Ronda Bransteitter, Linda Chelico, Udayaditya Sen and Pro- fessors Raymond Stevens and Myron Goodman appears in the online edition of the journal Nature.

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