Affiliation:
1. Mikrobiologie, Institut für Biologie II, Albert-Ludwigs-Universität Freiburg, Germany
2. Department of Microbiology, The Ohio State University, 484 West 12th Avenue, Columbus Ohio 43210
Abstract
ABSTRACT
A modified 3-hydroxypropionate cycle has been proposed as the autotrophic CO
2
fixation pathway for the thermoacidophilic crenarchaeon
Metallosphaera sedula
. The cycle requires the reductive conversion of 3-hydroxypropionate to propionyl-coenzyme A (propionyl-CoA). The specific activity of the 3-hydroxypropionate-, CoA-, and MgATP-dependent oxidation of NADPH in autotrophically grown cells was 0.023 μmol min
−1
mg protein
−1
. The reaction sequence is catalyzed by at least two enzymes. The first enzyme, 3-hydroxypropionyl-CoA synthetase, catalyzes the following reaction: 3-hydroxypropionate + ATP + CoA → 3-hydroxypropionyl-CoA + AMP + PP
i
. The enzyme was purified 95-fold to a specific activity of 18 μmol min
−1
mg protein
−1
from autotrophically grown
M. sedula
cells. An internal peptide sequence was determined and a gene encoding a homologous protein identified in the genome of
Sulfolobus tokodaii
; similar genes were found in
S. solfataricus
and
S. acidocaldarius
. The gene was heterologously expressed in
Escherichia coli
, and the His-tagged protein was purified. Both the native enzyme from
M. sedula
and the recombinant enzyme from
S. tokodaii
not only activated 3-hydroxypropionate to its CoA ester but also activated propionate, acrylate, acetate, and butyrate; however, with the exception of propionate, the affinities for these substrates were reduced. 3-Hydroxypropionyl-CoA synthetase is up-regulated eightfold in autotrophically versus heterotrophically grown
M. sedula
, supporting its proposed role during CO
2
fixation in this archaeon and possibly other members of the
Sulfolobaceae
family.
Publisher
American Society for Microbiology
Subject
Molecular Biology,Microbiology
Cited by
43 articles.
订阅此论文施引文献
订阅此论文施引文献,注册后可以免费订阅5篇论文的施引文献,订阅后可以查看论文全部施引文献