Kato Yoshihisa, Nishiyama Ken-ichi, Tokuda Hajime
Institute of Molecular and Cellular Biosciences, University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-0032, Japan.
FEBS Lett. 2003 Aug 28;550(1-3):114-8. doi: 10.1016/s0014-5793(03)00847-0.
SecA and an apparatus comprising SecYEG and SecDF-YajC complexes catalyze protein translocation across the Escherichia coli membrane. SecDF-YajC and SecG facilitate membrane insertion of SecA, which is the driving force for protein translocation. Here we report that SecDF-YajC depletion together with SecG depletion nearly completely inhibits protein translocation both in vivo and in vitro, although SecDF-YajC had been thought to be unnecessary for in vitro translocation. The level of SecG in membranes decreased to about half upon SecDF-YajC depletion and recovered to a normal level when SecDF-YajC was expressed. SecDF-YajC inhibited disulfide bond formation between two SecG molecules possessing a single cysteine residue. These results suggest functional interaction between SecDF-YajC and SecG.
SecA以及由SecYEG和SecDF - YajC复合物组成的装置催化蛋白质跨大肠杆菌膜的转运。SecDF - YajC和SecG促进SecA插入膜中，而SecA是蛋白质转运的驱动力。在此我们报告，尽管一直认为SecDF - YajC对于体外转运并非必需，但SecDF - YajC缺失与SecG缺失一起几乎完全抑制了体内和体外的蛋白质转运。SecDF - YajC缺失时，膜中SecG的水平降至约一半，而当SecDF - YajC表达时又恢复到正常水平。SecDF - YajC抑制了两个含有单个半胱氨酸残基的SecG分子之间二硫键的形成。这些结果表明SecDF - YajC与SecG之间存在功能相互作用。
