YidC mediates membrane protein insertion in bacteria

Rcjohnsen rcjohnsen at aol.com
Fri Aug 11 23:58:28 EST 2000


Nature 406, 637 - 641 (2000) © Macmillan Publishers Ltd. 
YidC mediates membrane protein insertion in bacteria
JAMES C. SAMUELSON*, MINYONG CHEN*, FENGLEI JIANG*, INES MÖLLER†,
MARTIN WIEDMANN†, ANDREAS KUHN‡, GREGORY J. PHILLIPS§ & ROSS E. DALBEY* 
* Department of Chemistry, The Ohio State University, 100 West 18th Avenue,
Columbus , Ohio 43210, USA
† Cellular Biochemistry and Biophysic Program, Memorial Sloan-Kettering Cancer
Centre, 1275 York Avenue , New York, New York 10021, USA
‡ University of Hohenheim, Institute for Microbiology and Molecular Biology,
Garbenstrasse 30, D-70599 Stuttgart, Germany
§ Department of Microbiology, Iowa State University, 207 Science I, Osborn
Drive, Ames, Iowa 50011, USA

Correspondence and requests for materials should be addressed to R.E.D.
(e-mail: dalbey at chemistry.ohio-state.edu).

The basic machinery for the translocation of proteins into or across membranes
is remarkably conserved from Escherichia coli to humans. In eukaryotes,
proteins are inserted into the endoplasmic reticulum using the signal
recognition particle (SRP) and the SRP receptor, as well as the integral
membrane Sec61 trimeric complex (composed of alpha, beta and gamma subunits)1.
In bacteria, most proteins are inserted by a related pathway that includes the
SRP homologue Ffh2-5, the SRP receptor FtsY6, 7, and the SecYEG trimeric
complex8, where Y and E are related to the Sec61 alpha and gamma subunits,
respectively. Proteins in bacteria that exhibit no dependence on the Sec
translocase were previously thought to insert into the membrane directly
without the aid of a protein machinery9, 10. Here we show that membrane
insertion of two Sec-independent proteins requires YidC. YidC is essential for
E. coli viability and homologues are present in mitochondria and chloroplasts.
Depletion of YidC also interferes with insertion of Sec-dependent membrane
proteins, but it has only a minor effect on the export of secretory proteins.
These results provide evidence for an additional component of the translocation
machinery that is specialized for the integration of membrane proteins.






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