Collier D N, Bankaitis V A, Weiss J B, Bassford P J
Department of Microbiology and Immunology, School of Medicine, University of North Carolina, Chapel Hill 27514.
Cell. 1988 Apr 22;53(2):273-83. doi: 10.1016/0092-8674(88)90389-3.
Evidence is presented that the E. coli secB gene encodes a soluble protein that interacts with the mature region of the precursor maltose-binding protein (MBP), and promotes MBP export by preventing premature folding of the newly synthesized polypeptide into an export-incompetent form. The interaction of SecB with MBP was indicated by the finding that synthesis of various export-defective MBP species interfered with normal protein export by limiting SecB availability. The antifolding activity of SecB was demonstrated by the following: the defect in MBP export in SecB- cells was suppressed by mutational alterations affecting MBP folding; export of a mutant MBP that is accomplished in a strictly posttranslational mode was totally blocked in SecB- cells; and the rate of folding of wild-type MBP synthesized in vitro was found to be accelerated when SecB was absent and greatly retarded when excess SecB was present.
有证据表明，大肠杆菌secB基因编码一种可溶性蛋白，该蛋白与前体麦芽糖结合蛋白（MBP）的成熟区域相互作用，并通过防止新合成的多肽过早折叠成无出口能力的形式来促进MBP的输出。SecB与MBP的相互作用通过以下发现得以表明：各种出口缺陷型MBP物种的合成通过限制SecB的可用性干扰了正常的蛋白质输出。SecB的抗折叠活性通过以下方式得以证明：影响MBP折叠的突变改变抑制了SecB缺陷型细胞中MBP输出的缺陷；以严格的翻译后模式完成的突变MBP的输出在SecB缺陷型细胞中被完全阻断；并且发现当不存在SecB时，体外合成的野生型MBP的折叠速率加快，而当存在过量SecB时则大大延迟。
