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Importance of transmembrane segments in Escherichia coli SecY

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Abstract

To assess the functional importance of the transmembrane regions of SecY, we constructed a series of SecY variants, in which the six central residues of each transmembrane segment were replaced by amino acid residues from either transmembrane segment 3 or 4 of LacY. The SecY function, as assessed by the ability to complement cold-sensitive secY mutants with respect to their growth and translocase defects, was eliminated by the alterations in transmembrane segments 2, 3, 4, 7, 9 and 10. Among them, those in segments 3 and 4 had especially severe effects. In contrast, transmembrane segments 1, 5, 6, and 8 were more tolerant to the sequence alterations. The purified protein with an altered transmembrane segment 6 retained, in large measure, the ability to support SecA-dependent preprotein translocation in vitro. These results will help us to further understand how the SecYEG protein translocation channel functions.

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Acknowledgments

We thank Yoshinori Akiyama for discussion, and Kiyoko Mochizuki, Mikihiro Yamada, and Yasuhide Yoshioka and Michiyo Sano for technical assistance. This work was supported by grants from CREST, JST (Japan Science and Technology Corporation), and the Ministry of Education, Culture, Sports, Science and Technology, Japan

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  1. Institute for Virus Research, Kyoto University, Sakyo-ku, 606-8507, Kyoto, Japan

    N. Shimokawa, H. Mori & K. Ito

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  1. N. Shimokawa
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  2. H. Mori
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  3. K. Ito
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Correspondence to K. Ito.

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Communicated by W. Goebel

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Shimokawa, N., Mori, H. & Ito, K. Importance of transmembrane segments in Escherichia coli SecY. Mol Gen Genomics 269, 180–187 (2003). https://doi.org/10.1007/s00438-003-0804-8

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  • DOI: https://doi.org/10.1007/s00438-003-0804-8

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