Characterization of a novel cullin5 binding domain in HIV-1 vif

Human immunodeficiency virus tyoe 1 (HIV-1) Vif counteracts host restriction cytidine deaminase (APOBEC3G) A3G by co-opting the cellular ubiquitin-proteasome machinery. Vif utilizes a viral-specific BC-box to recruit ElonginB-ElonginC and a novel zinc-binding HCCH motif to recruit Cullin5 (Cul5) to form an E3 ubiquitin ligase targeting A3G for polyubiquitination and subsequently proteasomal degradation. To determine the structural requirements in HIV-1 Vif HCCH motif for Cu15 binding and Vif function, we investigated the arrangement of the His and Cys residues, the role of the spacing between them, and the requirement for the conserved residues. Our data demonstrate that exchanging Cys for His and vice versa in the highly conserved Zn-coordinating HCCH motif disrupted Vif function and interaction with Cu15. Moreover, the maintenance of both conserved residues and spacing within the HCCH motif is critical for Vif function. We have identified a "viral Cu15 box" with consensus Hx2YFxCFx4 Phi x2A Phi x7-8Cx5H that is required for Cu15 selection and subsequent A3G degradation. This novel motif may represent a potential new target for anti-viral drug development. (c) 2007 Published by Elsevier Ltd.