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J. Bacteriol., 04 1996, 2368-2374, Vol 178, No. 8
S Thiemermann, J Dernedde, M Bernhard, W Schroeder, C Massanz and B Friedrich
Two open reading frames (ORFs) were identified immediately downstream of
the four structural genes for the soluble hydrogenase (SH) of Alcaligenes
eutrophus H16. While a mutation in ORF2 had no obvious effect on hydrogen
metabolism, an in-frame deletion in ORF1, subsequently designated hoxW, led
to a complete loss of SH activity and hence a significant retardation of
autotrophic growth on hydrogen. Hydrogen oxidation in the hoxW mutant was
catalyzed by the second hydrogenase, a membrane-bound enzyme. Assembly of
the four subunits of the SH was blocked in mutant cells, and HoxH, the
hydrogen-activating subunit, accumulated as a precursor which was still
capable of binding nickel. Protein sequencing revealed that HoxH isolated
from the wild type terminates at His-464, whereas the C-terminal amino acid
sequence of HoxH from the hoxW mutant is colinear with the deduced
sequence. Processing of the HoxH precursor was restored in vitro by a cell
extract containing HoxW. These results indicate that HoxW is a highly
specific carboxyl-terminal protease which releases a 24-amino-acid peptide
from HoxH prior to progression of subunit assembly.
Copyright © 1996, American Society for Microbiology
Carboxyl-terminal processing of the cytoplasmic NAD-reducing hydrogenase of Alcaligenes eutrophus requires the hoxW gene product
Institut fur Pflanzenphysiologie und Mikrobiologie, Freie Universitat Berlin, Germany.
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