Mutations in fliK and flhB affecting flagellar hook and filament assembly in Salmonella typhimurium.
Mutations in fliK and flhB affecting flagellar hook and filament assembly in Salmonella typhimurium.
复制标题
fliK 和 flhB 突变影响鼠伤寒沙门氏菌鞭毛钩和丝组装。
DOI：
10.1128/jb.178.10.2960-2970.1996
复制
发表时间：
1996
影响因子：
3.2
通讯作者：
Macnab,RM
中科院分区：
文献类型：
--
作者：
Williams,AW;Yamaguchi,S;Togashi,F;Aizawa,SI;Kawagishi,I;Macnab,RM
鼠伤寒沙门氏菌fliK基因的突变通常导致不能终止钩状组装和启动细丝组装（多钩表型）。多钩突变体产生假回复突变体，其在钩终止中仍然有缺陷，但已经恢复了组装细丝的能力（多钩细丝表型）。已发现多钩突变是移码或无义的，导致FliK的C末端截短。移码突变的基因内抑制因子被发现是恢复原始框架（因此C-末端序列）的抑制因子，但在大多数情况下，天然序列大量丢失，有时引入人工序列;在任何情况下，当C-末端区域内仍存在显著破坏时，都不会发生基因内抑制。通过使用一种新的PCR方案，框内缺失影响的N-末端和中心区域的FliK的构建和所得的表型进行了检查。小的缺失导致几乎正常的钩长度控制和几乎野生型群集。较大的缺失导致失去对钩长度的控制和较差的群集。最大的缺失严重影响细丝组装以及钩长度控制。基因外抑制基因定位于一个非连锁基因flhB，它编码一个完整的膜蛋白（T。Hirano，S.山口K. Oosawa和S.- I. Aizawa，J. Bacteriol. 176：5439-5449，1994; K. Kutsukake，T. Minamino和T. Yokoseki，J. Bacteriol. 176：7625-7629，1994）。它们要么是FlhB的C-末端胞质区域中的点突变，要么是靠近C末端的移码或无义突变。根据这些和其他可用的数据讨论了钩和细丝组装的过程以及FliK和FlhB在这些过程中的作用。我们认为，FliK措施钩长度，并在适当的点，发送信号到FlhB切换的底物特异性出口从钩蛋白晚期蛋白质，如鞭毛蛋白。
Mutations in the fliK gene of Salmonella typhimurium commonly cause failure to terminate hook assembly and initiate filament assembly (polyhook phenotype). Polyhook mutants give rise to pseudorevertants which are still defective in hook termination but have recovered the ability to assemble filament (polyhook-filament phenotype). The polyhook mutations have been found to be either frameshift or nonsense, resulting in truncation of the C terminus of FliK. Intragenic suppressors of frameshift mutations were found to be ones that restored the original frame (and therefore the C-terminal sequence), but in most cases with substantial loss of natural sequence and sometimes the introduction of artificial sequence; in no cases did intragenic suppression occur when significant disruption remained within the C-terminal region. By use of a novel PCR protocol, in-frame deletions affecting the N-terminal and central regions of FliK were constructed and the resulting phenotypes were examined. Small deletions resulted in almost normal hook length control and almost wild-type swarming. Larger deletions resulted in loss of control of hook length and poor swarming. The largest deletions severely affected filament assembly as well as hook length control. Extragenic suppressors map to an unlinked gene, flhB, which encodes an integral membrane protein (T. Hirano, S. Yamaguchi, K. Oosawa, and S.-I. Aizawa, J. Bacteriol. 176:5439-5449, 1994; K. Kutsukake, T. Minamino, and T. Yokoseki, J. Bacteriol. 176:7625-7629, 1994). They were either point mutations in the C-terminal cytoplasmic region of FlhB or frameshift or nonsense mutations close to the C terminus. The processes of hook and filament assembly and the roles of FliK and FlhB in these processes are discussed in light of these and other available data. We suggest that FliK measures hook length and, at the appropriate point, sends a signal to FlhB to switch the substrate specificity of export from hook protein to late proteins such as flagellin.