Patterson Hayley M, Brannigan James A, Cutting Simon M, Wilson Keith S, Wilkinson Anthony J, Ab Eiso, Diercks Tammo, de Jong Rob N, Truffault Vincent, Folkers Gert E, Kaptein Robert
Structural Biology Laboratory, Department of Chemistry, University of York, York YO10 5YW, United Kingdom.
J Biol Chem. 2005 Oct 28;280(43):36214-20. doi: 10.1074/jbc.M506910200. Epub 2005 Jul 27.
Sporulation in Bacillus subtilis begins with an asymmetric cell division giving rise to smaller forespore and larger mother cell compartments. Different programs of gene expression are subsequently directed by compartment-specific RNA polymerase sigma-factors. In the final stages, spore coat proteins are synthesized in the mother cell under the control of RNA polymerase containing sigma(K), (Esigma(K)). sigma(K) is synthesized as an inactive zymogen, pro-sigma(K), which is activated by proteolytic cleavage. Processing of pro-sigma(K) is performed by SpoIVFB, a metalloprotease that resides in a complex with SpoIVFA and bypass of forespore (Bof)A in the outer forespore membrane. Ensuring coordination of events taking place in the two compartments, pro-sigma(K) processing in the mother cell is delayed until appropriate signals are received from the forespore. Cell-cell signaling is mediated by SpoIVB and BofC, which are expressed in the forespore and secreted to the intercompartmental space where they regulate pro-sigma(K) processing by mechanisms that are not yet fully understood. Here we present the three-dimensional structure of BofC determined by solution state NMR. BofC is a monomer made up of two domains. The N-terminal domain, containing a four-stranded beta-sheet onto one face of which an alpha-helix is packed, closely resembles the third immunoglobulin-binding domain of protein G from Streptococcus. The C-terminal domain contains a three-stranded beta-sheet and three alpha-helices in a novel domain topology. The sequence connecting the domains contains a conserved DISP motif to which mutations that affect BofC activity map. Possible roles for BofC in the sigma(K) checkpoint are discussed in the light of sequence and structure comparisons.
枯草芽孢杆菌中的孢子形成始于不对称细胞分裂，产生较小的前芽孢和较大的母细胞区室。随后，不同的基因表达程序由区室特异性RNA聚合酶σ因子指导。在最后阶段，芽孢衣蛋白在母细胞中由含有σ（K）的RNA聚合酶（Esigma（K））控制下合成。σ（K）以无活性的酶原形式合成，即前体σ（K），通过蛋白水解切割被激活。前体σ（K）的加工由SpoIVFB进行，SpoIVFB是一种金属蛋白酶，它与SpoIVFA和前芽孢外膜中的前芽孢旁路（Bof）A形成复合物。为确保两个区室中发生的事件协调进行，母细胞中的前体σ（K）加工会延迟，直到从前芽孢接收到适当信号。细胞间信号传导由SpoIVB和BofC介导，它们在前芽孢中表达并分泌到区室间空间，在那里它们通过尚未完全理解的机制调节前体σ（K）的加工。在这里，我们展示了通过溶液状态核磁共振确定的BofC的三维结构。BofC是由两个结构域组成的单体。N端结构域包含一个四链β折叠，其一面堆积着一个α螺旋，与来自链球菌的蛋白G的第三个免疫球蛋白结合结构域非常相似。C端结构域包含一个三链β折叠和三个α螺旋，具有新颖的结构域拓扑结构。连接结构域的序列包含一个保守的DISP基序，影响BofC活性的突变定位在此基序上。根据序列和结构比较，讨论了BofC在σ（K）检查点中的可能作用。
