Department of Biochemistry and Molecular Biology, Uniformed Services University of the Health Sciences, Bethesda, Maryland 20814, United States.
Biochemistry. 2012 Mar 13;51(10):2078-86. doi: 10.1021/bi201738a. Epub 2012 Mar 5.
HIV-1 Vif is an accessory protein that induces the proteasomal degradation of the host restriction factor, apolipoprotein B mRNA-editing enzyme catalytic polypeptide-like 3G (APOBEC3G). The N-terminal half of Vif binds to APOBEC3G, and the C-terminal half binds to subunits of a cullin 5-based ubiquitin ligase. This Vif-directed ubiquitin ligase induces the degradation of APOBEC3G (a cytidine deaminase) and thereby protects the viral genome from mutation. A conserved PPLP motif near the C-terminus of Vif is essential for Vif function and is also involved in Vif oligomerization. However, the mechanism and functional significance of Vif oligomerization is unclear. We employed analytical ultracentrifugation to examine the oligomeric properties of Vif in solution. Contrary to previous reports, we find that Vif oligomerization does not require the conserved PPLP motif. Instead, our data suggest a more complex mechanism involving interactions among the HCCH motif, the BC box, and downstream residues in Vif. Mutation of residues near the PPLP motif (S165 and V166) affected the oligomeric properties of Vif and weakened the ability of Vif to bind and induce the degradation of APOBEC3G. We propose that Vif oligomerization may represent a mechanism for regulating interactions with APOBEC3G.
HIV-1 Vif 是一种辅助蛋白，可诱导宿主限制因子载脂蛋白 B mRNA 编辑酶催化多肽样 3G（APOBEC3G）的蛋白酶体降解。Vif 的 N 端半部分与 APOBEC3G 结合，C 端半部分与基于 cullin 5 的泛素连接酶的亚基结合。这种 Vif 定向的泛素连接酶诱导 APOBEC3G（胞嘧啶脱氨酶）的降解，从而保护病毒基因组免受突变。Vif 近 C 端的保守 PPLP 基序对于 Vif 功能至关重要，并且还参与 Vif 寡聚化。然而，Vif 寡聚化的机制和功能意义尚不清楚。我们采用分析超速离心法研究了 Vif 在溶液中的寡聚性质。与先前的报道相反，我们发现 Vif 寡聚化不需要保守的 PPLP 基序。相反，我们的数据表明，一种更复杂的机制涉及 HCCH 基序、BC 盒和 Vif 下游残基之间的相互作用。靠近 PPLP 基序（S165 和 V166）的残基突变影响了 Vif 的寡聚性质，并削弱了 Vif 结合和诱导 APOBEC3G 降解的能力。我们提出，Vif 寡聚化可能代表一种调节与 APOBEC3G 相互作用的机制。
