Barkocy-Gallagher G A, Cannon J G, Bassford P J
Department of Microbiology and Immunology, School of Medicine, University of North Carolina, Chapel Hill 27599-7290.
J Bacteriol. 1994 Jun;176(11):3397-9. doi: 10.1128/jb.176.11.3397-3399.1994.
Maltose-binding protein (MBP) is translocated across the cytoplasmic membrane of Escherichia coli; successful export depends on information in both the signal peptide and the mature moiety of the protein. To determine the shortest portion of the mature region that would maintain detectable entry of MBP into the export pathway, we took advantage of the properties of an MBP species with proline substituted in the +1 position relative to the cleavage site (MBP27-P). This protein efficiently crosses the cytoplasmic membrane but is not processed and acts as a competitive inhibitor of signal peptidase I (leader peptidase). Export of MBP27-P is measured by the inhibition of processing of other proteins, such as ribose-binding protein (RBP). A series of truncated derivatives of MBP27-P were tested for the ability to inhibit processing of RBP. An MBP27-P species with only 33 amino acids of the mature moiety inhibited processing of RBP, indicating that this truncated polypeptide was probably exported and interacted with signal peptidase I.
麦芽糖结合蛋白（MBP）可转运穿过大肠杆菌的细胞质膜；其成功输出取决于信号肽和蛋白质成熟部分中的信息。为了确定成熟区域中能够维持MBP进入输出途径且可检测到的最短部分，我们利用了一种MBP变体的特性，该变体在相对于切割位点的+1位置被脯氨酸取代（MBP27-P）。这种蛋白质能有效地穿过细胞质膜，但不会被加工，并且作为信号肽酶I（前导肽酶）的竞争性抑制剂发挥作用。通过抑制其他蛋白质（如核糖结合蛋白（RBP））的加工来测定MBP27-P的输出。测试了一系列MBP27-P的截短衍生物抑制RBP加工的能力。一种仅具有成熟部分33个氨基酸的MBP27-P变体抑制了RBP的加工，这表明这种截短的多肽可能被输出并与信号肽酶I相互作用。
