Affiliation:
1. Institut für Biotechnologie 1, Forschungszentrum Jülich GmbH, D-52425 Jülich,1 and
2. Lehrstuhl für Genetik, Universität Bayreuth, D-95440 Bayreuth,2 Germany
Abstract
ABSTRACT
The bacterial twin arginine translocation (Tat) pathway translocates across the cytoplasmic membrane folded proteins which, in most cases, contain a tightly bound cofactor. Specific amino-terminal signal peptides that exhibit a conserved amino acid consensus motif, S/T-R-R-X-F-L-K, direct these proteins to the Tat translocon. The glucose-fructose oxidoreductase (GFOR) of
Zymomonas mobilis
is a periplasmic enzyme with tightly bound NADP as a cofactor. It is synthesized as a cytoplasmic precursor with an amino-terminal signal peptide that shows all of the characteristics of a typical twin arginine signal peptide. However, GFOR is not exported to the periplasm when expressed in the heterologous host
Escherichia coli
, and enzymatically active pre-GFOR is found in the cytoplasm. A precise replacement of the pre-GFOR signal peptide by an authentic
E. coli
Tat signal peptide, which is derived from pre-trimethylamine
N
-oxide (TMAO) reductase (TorA), allowed export of GFOR, together with its bound cofactor, to the
E. coli
periplasm. This export was inhibited by carbonyl cyanide
m
-chlorophenylhydrazone, but not by sodium azide, and was blocked in
E. coli tatC
and
tatAE
mutant strains, showing that membrane translocation of the TorA-GFOR fusion protein occurred via the Tat pathway and not via the Sec pathway. Furthermore, tight cofactor binding (and therefore correct folding) was found to be a prerequisite for proper translocation of the fusion protein. These results strongly suggest that Tat signal peptides are not universally recognized by different Tat translocases, implying that the signal peptides of Tat-dependent precursor proteins are optimally adapted only to their cognate export apparatus. Such a situation is in marked contrast to the situation that is known to exist for Sec-dependent protein translocation.
Publisher
American Society for Microbiology
Subject
Molecular Biology,Microbiology
Cited by
61 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