Molecular sieve mechanism of selective release of cytoplasmic proteins by osmotically shocked Escherichia coli

Vasquez-Laslop, N Lee, H Hu, R Neyfakh, AA

N. Vasquez-laslop et al., Molecular sieve mechanism of selective release of cytoplasmic proteins by osmotically shocked Escherichia coli, J BACT, 183(8), 2001, pp. 2399-2404

24

INGLESE

Article

Microbiology

JOURNAL OF BACTERIOLOGY

0021-9193 → ACNP

183

8

2001

2399 - 2404

ISI

0021-9193(200104)183:8<2399:MSMOSR>2.0.ZU;2-R

Escherichia coli cells, the outer membrane of which is permeabilized with E DTA, release a specific subset of cytoplasmic proteins upon a sudden drop i n osmolarity in the surrounding medium. This subset includes EF-Tu, thiored oxin, and DnaK among other proteins, and comprises similar to 10% of the to tal bacterial protein content. As we demonstrate here, the same proteins ar e 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 ab le to pass through a 100-kDa-cutoff cellulose membrane upon molecular filtr ation of an E. coli homogenate. This finding indicates that in osmotically shocked or electroporated bacteria, proteins are strained through a molecul ar sieve formed by the transiently damaged bacterial envelope. As a result, proteins of small native sizes are selectively released, whereas large pro teins and large protein complexes are retained by bacterial cells.