MOTILITY PROTEIN INTERACTIONS IN THE BACTERIAL FLAGELLAR MOTOR
MOTILITY PROTEIN INTERACTIONS IN THE BACTERIAL FLAGELLAR MOTOR
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DOI：
10.1073/pnas.92.6.1970
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发表时间：
1995-03-14
影响因子：
11.1
通讯作者：
MANSON, MD
中科院分区：
文献类型：
--
作者：
GARZA, AG;HARRISHALLER, LW;MANSON, MD
五种蛋白质（MotA、MotB、FliG、FliM 和 FliN）与大肠杆菌和鼠伤寒沙门氏菌鞭毛旋转的激发有关。鞭毛功能的一种模型设想 MotA 和 MotB 构成旋转电机的定子，而 FliG、FliM 和 FliN 是转子的一部分。 MotA 可能充当跨膜质子通道，MotB 已被提议将 MotA 锚定到细胞壁的肽聚糖上。为了研究 Mot 蛋白本身之间以及它们与鞭毛运动其他组件之间的相互作用，我们尝试分离 13 个显性或部分显性 motB 错义突变的基因外抑制子。其中四个产生了抑制器，其抑制效率差异很大。抑制模式是部分等位基因特异性的，但没有抑制子严重损害 motB(+) 菌株的运动性。在最初选择的 20 个抑制因子中，有 15 个通过 DNA 测序进行了鉴定。其中 14 个会导致 MotA 中的单个氨基酸发生变化。 13 个位于 MotA 推定周质环中或直接邻近的残基之后，剩下的一个改变了 MotA 的第四个预测跨膜螺旋中间的残基。我们得出结论，MotA 和 MotB 蛋白形成复合物，并且它们的相互作用直接涉及 MotA 的周质环或受 MotA 的周质环的强烈影响。最初选择的第 15 个抑制子和在随后的搜索过程中鉴定出的 2 个 motB 抑制子导致 FliG 中的单个氨基酸取代。这一发现表明，假设的 Mot-蛋白复合物可能与鞭毛电机定子-转子界面上的 FliG 非常接近。
Five proteins (MotA, MotB, FliG, FliM, and FliN) have been implicated in energizing flagellar rotation in Escherichia coli and Salmonella typhimurium. One model for flagellar function envisions that MotA and MotB comprise the stator of a rotary motor and that FliG, FliM, and FliN are part of the rotor. MotA probably functions as a transmembrane proton channel, and MotB has been proposed to anchor MotA to the peptidoglycan of the cell wall. To study interactions between the Mot proteins themselves and between them and other components of the flagellar motor, we attempted to isolate extragenic suppressors of 13 dominant or partially dominant motB missense mutations. Four of these yielded suppressors, which exhibited widely varying efficiencies of suppression. The pattern of suppression was partially allele-specific, but no suppressor seriously impaired motility in a motB(+) strain. Of 20 suppressors from the original selection, 15 were characterized by DNA sequencing. Fourteen of these cause single amino acid changes in MotA. Thirteen after residues in, or directly adjacent to, the putative periplasmic loops of MotA, and the remaining one alters a residue in the middle of the fourth predicted transmembrane helix of MotA. We conclude that the MotA and MotB proteins form a complex and that their interaction directly involves or is strongly influenced by the periplasmic loops of MotA. The 15th suppressor from the original selection and 2 motB suppressors identified during a subsequent search cause single amino acid substitutions in FliG. This finding suggests that the postulated Mot-protein complex may be in close proximity to FliG at the stator-rotor interface of the flagellar motor.