Fan Chun-Yang, Lee Soojin, Ren Hong-Yu, Cyr Douglas M
Department of Cell and Developmental Biology, School of Medicine, University of North Carolina, Chapel Hill, North Carolina 27599-7090, USA.
Mol Biol Cell. 2004 Feb;15(2):761-73. doi: 10.1091/mbc.e03-03-0146. Epub 2003 Dec 2.
Hsp40 family members regulate Hsp70s ability to bind nonnative polypeptides and thereby play an essential role in cell physiology. Type I and type II Hsp40s, such as yeast Ydj1 and Sis1, form chaperone pairs with cytosolic Hsp70 Ssa1 that fold proteins with different efficiencies and carry out specific cellular functions. The mechanism by which Ydj1 and Sis1 specify Hsp70 functions is not clear. Ydj1 and Sis1 share a high degree of sequence identity in their amino and carboxyl terminal ends, but each contains a structurally unique and centrally located protein module that is implicated in chaperone function. To test whether the chaperone modules of Ydj1 and Sis1 function in the specification of Hsp70 action, we constructed a set of chimeric Hsp40s in which the chaperone domains of Ydj1 and Sis1 were swapped to form YSY and SYS. Purified SYS and YSY exhibited protein-folding activity and substrate specificity that mimicked that of Ydj1 and Sis1, respectively. In in vivo studies, YSY exhibited a gain of function and, unlike Ydj1, could complement the lethal phenotype of sis1 Delta and facilitate maintenance of the prion [RNQ+]. Ydj1 and Sis1 contain exchangeable chaperone modules that assist in specification of Hsp70 function.
热休克蛋白40（Hsp40）家族成员调节热休克蛋白70（Hsp70）结合非天然多肽的能力，从而在细胞生理学中发挥重要作用。I型和II型Hsp40，如酵母Ydj1和Sis1，与胞质Hsp70 Ssa1形成伴侣对，以不同效率折叠蛋白质并执行特定的细胞功能。Ydj1和Sis1确定Hsp70功能的机制尚不清楚。Ydj1和Sis1在其氨基和羧基末端具有高度的序列同一性，但每个都包含一个结构独特且位于中央的蛋白质模块，该模块与伴侣功能有关。为了测试Ydj1和Sis1的伴侣模块在Hsp70作用的特异性中是否起作用，我们构建了一组嵌合Hsp40，其中Ydj1和Sis1的伴侣结构域被交换以形成YSY和SYS。纯化的SYS和YSY分别表现出模仿Ydj1和Sis1的蛋白质折叠活性和底物特异性。在体内研究中，YSY表现出功能获得，并且与Ydj1不同，它可以补充sis1Δ的致死表型并促进朊病毒[RNQ+]的维持。Ydj1和Sis1包含可交换的伴侣模块，可以帮助确定Hsp70的功能。
