Ramer Sandra W, Schoolnik Gary K, Wu Cheng-Yen, Hwang Jaiweon, Schmidt Sarah A, Bieber David
Department of Medicine (Infectious Diseases and Geographic Medicine) and Microbiology & Immunology, Stanford Medical School, Stanford, California 94305, USA.
J Bacteriol. 2002 Jul;184(13):3457-65. doi: 10.1128/JB.184.13.3457-3465.2002.
Production of type IV bundle-forming pili (BFP) by enteropathogenic Escherichia coli (EPEC) requires the protein products of 12 genes of the 14-gene bfp operon. Antisera against each of these proteins were used to demonstrate that in-frame deletion of individual genes within the operon reduces the abundance of other bfp operon-encoded proteins. This result was demonstrated not to be due to downstream polar effects of the mutations but rather was taken as evidence for protein-protein interactions and their role in the stabilization of the BFP assembly complex. These data, combined with the results of cell compartment localization studies, suggest that pilus formation requires the presence of a topographically discrete assembly complex that is composed of BFP proteins in stoichiometric amounts. The assembly complex appears to consist of an inner membrane component containing three processed, pilin-like proteins, BfpI, -J, and -K, that localize with BfpE, -L, and -A (the major pilin subunit); an outer membrane, secretin-like component, BfpB and -G; and a periplasmic component composed of BfpU. Of these, only BfpL consistently localizes with both the inner and outer membranes and thus, together with BfpU, may articulate between the Bfp proteins in the inner membrane and outer membrane compartments.
肠致病性大肠杆菌（EPEC）IV型束状菌毛（BFP）的产生需要14个基因的bfp操纵子中的12个基因的蛋白质产物。针对这些蛋白质中的每一种的抗血清被用于证明操纵子内单个基因的框内缺失会降低其他bfp操纵子编码的蛋白质的丰度。这一结果被证明不是由于突变的下游极性效应，而是被视为蛋白质-蛋白质相互作用及其在BFP组装复合物稳定中的作用的证据。这些数据，结合细胞区室定位研究的结果，表明菌毛形成需要存在一个由化学计量的BFP蛋白组成的拓扑学上离散的组装复合物。组装复合物似乎由一个内膜组分组成，该组分包含三种经过加工的、菌毛蛋白样蛋白BfpI、-J和-K，它们与BfpE、-L和-A（主要菌毛亚基）定位在一起；一个外膜、分泌素样组分BfpB和-G；以及一个由BfpU组成的周质组分。其中，只有BfpL始终与内膜和外膜定位在一起，因此，它可能与BfpU一起在内膜和外膜区室的Bfp蛋白之间起连接作用。
