MotD of Sinorhizobium meliloti and related α-proteobacteria is the flagellar-hook-length regulator and therefore reassigned as FliK
MotD of Sinorhizobium meliloti and related α-proteobacteria is the flagellar-hook-length regulator and therefore reassigned as FliK
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DOI：
10.1128/jb.188.6.2144-2153.2006
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发表时间：
2006-03-01
影响因子：
3.2
通讯作者：
Scharf, B
中科院分区：
文献类型：
--
作者：
Eggenhofer, E;Rachel, R;Scharf, B
土壤细菌苜蓿中华根瘤菌的鞭毛在复杂的细丝结构和鞭毛旋转速度的调节方面不同于肠道细菌范例。紫花苜蓿的运动控制模式与两个新的周质运动蛋白MotC和Mote有一个分子推论，这两个蛋白除了普遍存在的MotA/MOTB能量质子通道外，还存在两个新的周质运动蛋白。第五个运动基因位于motb和motC基因下游的mot操纵子中。它的基因产物最初被命名为MotD，一种功能未知的细胞质运动蛋白。在此，我们将MotD重新指定为鞭毛钩长的调节者Flik。Flik基因是苜蓿链霉菌鞭毛调节基因中为数不多的未被注释的基因之一。作为其类的特征，475个残基的Flik蛋白在其羧基末端区域包含一个保守的紧密折叠的Flg钩区。Flik的缺失会导致缺少细丝结构的长鞭毛钩(多钩)的形成。基因外抑制突变都定位在跨膜输出蛋白FlhB的细胞质区域，并在多钩存在的情况下恢复鞭毛细丝的组装，从而恢复运动。Flik的结构特性与其作为鞭毛输出装置的底物特异性开关的功能是一致的，该开关可以从杆状/钩型底物切换到细丝型底物。
The flagella of the soil bacterium Sinorhizobium meliloti differ from the enterobacterial paradigm in the complex filament structure and modulation of the flagellar rotary speed. The mode of motility control in S. meliloti has a molecular corollary in two novel periplasmic motility proteins, MotC and MotE, that are present in addition to the ubiquitous MotA/MotB energizing proton channel. A fifth motility gene is located in the mot operon downstream of the motB and motC genes. Its gene product was originally designated MotD, a cytoplasmic motility protein having an unknown function. We report here reassignment of MotD as FliK, the regulator of flagellar hook length. The FliK gene is one of the few flagellar genes not annotated in the contiguous flagellar regulon of S. meliloti. Characteristic for its class, the 475-residue FliK protein contains a conserved, compactly folded Flg hook domain in its carboxy-terminal region. Deletion of fliK leads to formation of prolonged flagellar hooks (polyhooks) with missing filament structures. Extragenic suppressor mutations all mapped in the cytoplasmic region of the transmembrane export protein FlhB and restored assembly of a flagellar filament, and thus motility, in the presence of polyhooks. The structural properties of FliK are consistent with its function as a substrate specificity switch of the flagellar export apparatus for switching from rod/hook-type substrates to filament-type substrates.