Laboratorium für Biochemie und Bayreuther Zentrum für Molekulare Biowissenschaften, Universität Bayreuth,D-95440 Bayreuth, Germany.
J Mol Biol. 2011 Feb 11;406(1):176-94. doi: 10.1016/j.jmb.2010.12.010. Epub 2010 Dec 13.
The SlyD (sensitive to lysis D) protein of Escherichia coli is a folding enzyme with a chaperone domain and a prolyl isomerase domain of the FK506 binding protein type. Here we investigated how the two domains and their interplay are optimized for function in protein folding. Unfolded protein molecules initially form a highly dynamic complex with the chaperone domain of SlyD, and they are then transferred to the prolyl isomerase domain. The turnover number of the prolyl isomerase site is very high and guarantees that, after transfer, prolyl peptide bonds in substrate proteins are isomerized very rapidly. The Michaelis constant of catalyzed folding reflects the substrate affinity of the chaperone domain, and the turnover number is presumably determined by the rate of productive substrate transfer from the chaperone to the prolyl isomerase site and by the intrinsic propensity of the refolding protein chain to leave the active site with the native prolyl isomer. The efficiency of substrate transfer is high because dissociation from the chaperone site is very fast and because the two sites are close to each other. Protein molecules that left the prolyl isomerase site with an incorrect prolyl isomer can rapidly be re-bound by the chaperone domain because the association rate is very high as well.
大肠杆菌的 SlyD（对裂解敏感 D）蛋白是一种折叠酶，具有 FK506 结合蛋白类型的伴侣域和脯氨酰异构酶域。在这里，我们研究了两个结构域及其相互作用如何针对蛋白质折叠的功能进行优化。未折叠的蛋白质分子最初与 SlyD 的伴侣结构域形成高度动态的复合物，然后被转移到脯氨酰异构酶结构域。脯氨酰异构酶位点的周转率非常高，可确保转移后，底物蛋白中的脯氨酰肽键迅速异构化。催化折叠的米氏常数反映了伴侣结构域的底物亲和力，而周转率大概取决于从伴侣结构域到脯氨酰异构酶位点的有产性底物转移的速率，以及折叠蛋白链具有离开具有天然脯氨酰异构的活性位点的固有倾向。底物转移的效率很高，因为从伴侣结构域解离非常快，并且两个结构域彼此靠近。带有错误脯氨酰异构体的离开脯氨酰异构酶位点的蛋白质分子可以迅速重新与伴侣结构域结合，因为缔合速率也非常高。
