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Roles of SecG in ATP- and SecA-dependent protein translocation.
Proc Natl Acad Sci U S A 1998; 95(23):13567-72PN

Abstract

SecA, the translocation ATPase in Escherichia coli, undergoes cycles of conformational changes (insertion/deinsertion) in response to ATP and a preprotein. The membrane-embedded portion of protein translocase, SecYEG, has crucial roles in the SecA-driven preprotein translocation reaction. We previously identified a secY mutation (secY205) that did not allow an ATP- and preprotein-dependent (productive) insertion of SecA as well as secA mutations that suppressed the secY205 translocation defect. One of the suppressor mutations, secA36, also suppressed the cold-sensitive phenotype of the secG deletion mutant. In vitro experiments at 20 degreesC showed that inverted membrane vesicles lacking SecG were almost inactive in combination with the wild-type SecA protein in translocation of proOmpA as well as in the accompanying ATP hydrolysis. In contrast, the SecA36 mutant protein was found to be able to execute the translocation activity fully at this temperature, even in the absence of SecG. A SecG requirement and its alleviation by the SecA36 alteration also were shown for the SecA insertion reaction. The finding that the SecA36 protein no longer requires assistance from SecG in its insertion and in its catalysis of protein translocation agrees with the idea that SecG normally assists in the functioning of SecA. In agreement with this notion, when the intrinsic SecA function was compromised by a lowered ATP concentration, SecG became essential even at 37 degreesC and even for the SecA36 protein. We propose that in the normal translocase, SecG cooperates with SecA to facilitate efficient movement of preprotein in each catalytic cycle of SecA.

Authors+Show Affiliations

Institute for Virus Research, Kyoto University, Sakyo-ku, Kyoto 606-8507, Japan.No affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

9811840

Citation

Matsumoto, G, et al. "Roles of SecG in ATP- and SecA-dependent Protein Translocation." Proceedings of the National Academy of Sciences of the United States of America, vol. 95, no. 23, 1998, pp. 13567-72.
Matsumoto G, Mori H, Ito K. Roles of SecG in ATP- and SecA-dependent protein translocation. Proc Natl Acad Sci USA. 1998;95(23):13567-72.
Matsumoto, G., Mori, H., & Ito, K. (1998). Roles of SecG in ATP- and SecA-dependent protein translocation. Proceedings of the National Academy of Sciences of the United States of America, 95(23), pp. 13567-72.
Matsumoto G, Mori H, Ito K. Roles of SecG in ATP- and SecA-dependent Protein Translocation. Proc Natl Acad Sci USA. 1998 Nov 10;95(23):13567-72. PubMed PMID: 9811840.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Roles of SecG in ATP- and SecA-dependent protein translocation. AU - Matsumoto,G, AU - Mori,H, AU - Ito,K, PY - 1998/11/13/pubmed PY - 1998/11/13/medline PY - 1998/11/13/entrez SP - 13567 EP - 72 JF - Proceedings of the National Academy of Sciences of the United States of America JO - Proc. Natl. Acad. Sci. U.S.A. VL - 95 IS - 23 N2 - SecA, the translocation ATPase in Escherichia coli, undergoes cycles of conformational changes (insertion/deinsertion) in response to ATP and a preprotein. The membrane-embedded portion of protein translocase, SecYEG, has crucial roles in the SecA-driven preprotein translocation reaction. We previously identified a secY mutation (secY205) that did not allow an ATP- and preprotein-dependent (productive) insertion of SecA as well as secA mutations that suppressed the secY205 translocation defect. One of the suppressor mutations, secA36, also suppressed the cold-sensitive phenotype of the secG deletion mutant. In vitro experiments at 20 degreesC showed that inverted membrane vesicles lacking SecG were almost inactive in combination with the wild-type SecA protein in translocation of proOmpA as well as in the accompanying ATP hydrolysis. In contrast, the SecA36 mutant protein was found to be able to execute the translocation activity fully at this temperature, even in the absence of SecG. A SecG requirement and its alleviation by the SecA36 alteration also were shown for the SecA insertion reaction. The finding that the SecA36 protein no longer requires assistance from SecG in its insertion and in its catalysis of protein translocation agrees with the idea that SecG normally assists in the functioning of SecA. In agreement with this notion, when the intrinsic SecA function was compromised by a lowered ATP concentration, SecG became essential even at 37 degreesC and even for the SecA36 protein. We propose that in the normal translocase, SecG cooperates with SecA to facilitate efficient movement of preprotein in each catalytic cycle of SecA. SN - 0027-8424 UR - https://www.unboundmedicine.com/medline/citation/9811840/Roles_of_SecG_in_ATP__and_SecA_dependent_protein_translocation_ L2 - http://www.pnas.org/cgi/pmidlookup?view=long&pmid=9811840 DB - PRIME DP - Unbound Medicine ER -