Azim M Kamran, Noor Sajid
H.E.J. Research Institute of Chemistry, International Center for Chemical Sciences, University of Karachi, Karachi, Pakistan.
Protein J. 2007 Jun;26(4):213-9. doi: 10.1007/s10930-006-9048-x.
HslVU, a two-component proteasome-related prokaryotic system is composed of HslV protease and HslU ATPase. HslV protomers assemble in a dodecamer of two-stacked hexameric rings that form a complex with HslU hexamers. The intra- and inter-ring protomer interfaces in the HslV dodecamer underpin the integrity and functionality of HslVU. Structural characterization of HslV from different bacteria illustrated considerable differences in interacting residues, accessible surface and gap volumes at the intra-ring interface that is primarily stabilized by polar interactions. Amino acid residues Lys28, Arg83 and Asp111 have envisaged as hot spots at this HslU-interacting interface. The inter-ring interfaces that are made up of side chain packing of hydrophobic residues are structurally conserved. Hyperthermostable bacterium T. maritima HslV has extensively networked polar/nonpolar interactions and highly packed environment at all interfaces. Present data demonstrates that HslV protomer interfaces perform distinct functions; whereas intra-ring interface participates in HslV:HslU interaction resulting in allosteric activation of HslV protease by HslU, the inter-ring interfaces uphold the oligomeric form of HslV.
HslVU是一种与蛋白酶体相关的双组分原核系统，由HslV蛋白酶和HslU ATP酶组成。HslV原体组装成由两个堆叠的六聚体环组成的十二聚体，该十二聚体与HslU六聚体形成复合物。HslV十二聚体中的环内和环间原体界面支撑着HslVU的完整性和功能性。来自不同细菌的HslV的结构表征表明，环内界面处相互作用的残基、可及表面和间隙体积存在显著差异，该界面主要由极性相互作用稳定。氨基酸残基Lys28、Arg83和Asp111被认为是该HslU相互作用界面的热点。由疏水残基的侧链堆积组成的环间界面在结构上是保守的。超嗜热细菌海栖热袍菌HslV在所有界面都有广泛的极性/非极性相互作用网络和高度密集的环境。目前的数据表明，HslV原体界面执行不同的功能；环内界面参与HslV:HslU相互作用，导致HslU对HslV蛋白酶的变构激活，而环间界面维持HslV的寡聚形式。
