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Chaperones specific for the membrane‐bound [NiFe]‐hydrogenase interact with the Tat signal peptide of the small subunit precursor in Ralstonia eutropha H16
Author(s) -
Schubert Torsten,
Lenz Oliver,
Krause Eberhard,
Volkmer Rudolf,
Friedrich Bärbel
Publication year - 2007
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.2007.05933.x
Subject(s) - periplasmic space , protein subunit , biology , cupriavidus necator , hydrogenase , ralstonia , biochemistry , cytoplasm , signal peptidase , signal peptide , twin arginine translocation pathway , membrane protein , microbiology and biotechnology , membrane , enzyme , peptide sequence , membrane transport protein , bacteria , gene , escherichia coli , genetics , polyhydroxyalkanoates
Summary Periplasmic membrane‐bound [NiFe]‐hydrogenases undergo a complex maturation pathway, including cofactor incorporation, subunit assembly, and finally twin‐arginine‐dependent membrane translocation (Tat). In this study, the role of the two accessory proteins HoxO and HoxQ in the maturation of the membrane‐bound [NiFe]‐hydrogenase (MBH) of Ralstonia eutropha H16 was investigated. MBH activity was absent in soluble as well as membrane fractions of cells with deletions in the respective genes. The absence of HoxO and HoxQ led to degradation of the small subunit precursor (preHoxK) of the MBH. The two accessory proteins directly interacted with preHoxK prior to assembly of active MBH dimer in the cytoplasm. MBH mutants with modified Tat signal peptides were disrupted in preHoxK/HoxO/HoxQ complex formation. Isolated HoxO and HoxQ proteins formed a complex in vitro with the chemically synthesized HoxK Tat signal peptide. Two functions of the two chaperones are discussed: (i) protection of the Fe–S cluster containing HoxK subunit under oxygenic conditions, and (ii) avoidance of HoxK export prior to dimerization with the large MBH subunit HoxG.