The Carboxyl-Terminal Region Is Essential for Sec-A Dimerization

Authors: Hirano M.; Matsuyama S.I.; Tokuda H.

Source: Biochemical and Biophysical Research Communications, Volume 229, Number 1, December 1996 , pp. 90-95(6)

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Abstract:

SecA, comprising 901 amino acid residues, exists as a dimer. By means of size exclusion chromatography and chemical cross-linking analysis, five truncated SecA derivatives were examined to identify the region of SecA essential for dimer formation. Among them, only N95 (Delta832-901) retained SecA activity. N95 existed as a dimer, indicating that the carboxyl-terminal three cysteine residues are dispensable for physiological dimerization. Both N76 (Delta675-901) and N66 (Delta583-901) existed as monomers. Monomeric N76 was able to bind to ATP, indicating that the dimerization of SecA is not a prerequisite for ATP binding. However, the rate of ATP hydrolysis by N76 was 25% of that by SecA. C53 (Delta1-437) and C28 (Delta1-661) formed dimers irrespective of the presence or absence of 2-mercaptoethanol. C28, but not C53, also existed as an oligomer in the absence of 2-mercaptoethanol, suggesting that the 438-661 region present in C53 prevents intermolecular disulfide bond formation at the carboxyl-terminal cysteine residue. From these results, the region essential for the physiological dimer formation was concluded to be located in the 662-831 region of SecA.

Language: English

Document Type: Research article

Affiliations: Institute of Molecular and Cellular Biosciences, The University of Tokyo, 1-1-1 Yayoi, Tokyo, 113, Japan

Publication date: 1996-12-01