The role of the twin-arginine motif in the signal peptide encoded by the hydA gene of the hydrogenase from Wolinella succinogenes |
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Authors: | Roland Gross Jörg Simon A Kröger |
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Institution: | Institut für Mikrobiologie, Johann Wolfgang Goethe-Universit?t, Marie-Curie-Stra?e 9, D-60439 Frankfurt am Main, Germany e-mail: a.kroeger@em.uni-frankfurt.de, Tel.: +49-69-79829507, Fax: +49-69-79829527, DE
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Abstract: | The hydABC operon of Wolinella succinogenes encodes the three subunits of the membrane-integrated Ni-hydrogenase. The catalytic subunit, HydB, is on the periplasmic
side of the membrane. Residues R41 and R42 of the twin-arginine motif within the signal peptide of the precursor of the iron-sulfur
subunit, HydA, were replaced by two glutamine residues. The corresponding mutant did not grow with H2 as the electron donor of anaerobic respiration. Mature HydB and the precursor protein of HydA were located exclusively in
the cytoplasmic cell fraction of the mutant, which catalyzed the reduction of benzyl viologen by H2, suggesting that HydB contained Ni. The HydC protein was located in the membrane fraction of the mutant in wild-type amounts.
HydC was purified and was shown to contain heme. The results suggest that HydA and HydB are translocated across the membrane
by the Tat (twin-arginine translocation) system. The translocation of HydA and HydB as well as the maturation of the precursor
protein of HydA appear to depend on the presence of the twin-arginine motif. In contrast, maturation of HydB, the insertion
of HydC into the membrane, and heme attachment to HydC are apparently independent of the twin-arginine motif and do not require
translocation of the two other hydrogenase subunits.
Received: 17 June 1999 / Accepted: 21 July 1999 |
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Keywords: | Ni-hydrogenase Cytochrome b Wolinella succinogenes Signal peptide Twin-arginine transfer Tat system |
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