Affiliation:
1. Center for Pharmaceutical Biotechnology, University of Illinois, Chicago, Illinois 60607
Abstract
ABSTRACT
Escherichia coli
cells, the outer membrane of which is permeabilized with EDTA, release a specific subset of cytoplasmic proteins upon a sudden drop in osmolarity in the surrounding medium. This subset includes EF-Tu, thioredoxin, and DnaK among other proteins, and comprises ∼10% of the total bacterial protein content. As we demonstrate here, the same proteins are released from electroporated
E. coli
cells pretreated with EDTA. Although known for several decades, the phenomenon of selective release of proteins has received no satisfactory explanation. Here we show that the subset of released proteins is almost identical to the subset of proteins that are able to pass through a 100-kDa-cutoff cellulose membrane upon molecular filtration of an
E. coli
homogenate. This finding indicates that in osmotically shocked or electroporated bacteria, proteins are strained through a molecular sieve formed by the transiently damaged bacterial envelope. As a result, proteins of small native sizes are selectively released, whereas large proteins and large protein complexes are retained by bacterial cells.
Publisher
American Society for Microbiology
Subject
Molecular Biology,Microbiology
Cited by
85 articles.
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