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research-article

Involvement of SecB, a chaperone, in the export of ribose-binding protein.

Department of Life Science, Korea Advanced Institute of Science and Technology, Yuseong-Ku, Daejun.

ABSTRACT

Ribose-binding protein (RBP) is an exported protein of Escherichia coli that functions in the periplasm. The export of RBP involves the secretion machinery of the cell, consisting of a cytoplasmic protein, SecA, and the integral membrane translocation complex, including SecE and SecY. SecB protein, a chaperone known to mediate the export of some periplasmic and outer membrane proteins, was previously reported not to be involved in RBP translocation even though small amounts of in vitro complexes between SecB and RBP have been detected. In our investigation, it was shown that a dependence on SecB could be demonstrated under conditions in which export was compromised. Species of RBP which carry two mutations, one in the leader that blocks export and a second in the mature protein which partially suppresses the export defect, were shown to be affected by SecB for efficient translocation. Five different changes which suppress the effect of the signal sequence mutation -17LP are all located in the N domain of the tertiary structure of RBP. All species of RBP show similar interaction with SecB. Furthermore, a leaky mutation, -14AE, generated by site-specific mutagenesis causes reduced export in the absence of SecB. These results indicate that SecB can interact with RBP during secretion, although it is not absolutely required under normal circumstances.

This article has been cited by other articles:

• Kim, J., Luirink, J., Kendall, D. A. (2000). SecB Dependence of an Exported Protein Is a Continuum Influenced by the Characteristics of the Signal Peptide or Early Mature Region. J. Bacteriol. 182: 4108-4112 [Abstract] [Full Text]  
• Berlyn, M. K. B. (1998). Linkage Map of Escherichia coli K-12, Edition 10: The Traditional Map. Microbiol. Mol. Biol. Rev. 62: 814-984 [Abstract] [Full Text]  
• Kim, J., Kendall, D. A. (1998). Identification of a Sequence Motif That Confers SecB Dependence on a SecB-Independent Secretory Protein In Vivo. J. Bacteriol. 180: 1396-1401 [Abstract] [Full Text]  
• Ahn, T., Kim, H. (1996). Differential Effect of Precursor Ribose Binding Protein of Escherichia coli and Its Signal Peptide on the SecA Penetration of Lipid Bilayer. J. Biol. Chem. 271: 12372-12379 [Abstract] [Full Text]