Effects of SecE depletion on the inner and outer membrane proteomes of Escherichia coli

TY - JOUR

T1 - Effects of SecE depletion on the inner and outer membrane proteomes of Escherichia coli

AU - Baars, Louise

AU - Wagner, Samuel

AU - Wickström, David

AU - Klepsch, Mirjam

AU - Ytterberg, A Jimmy

AU - van Wijk, Klaas J

AU - de Gier, Jan-Willem

PY - 2008/5

Y1 - 2008/5

N2 - The Sec translocon is a protein-conducting channel that allows polypeptides to be transferred across or integrated into a membrane. Although protein translocation and insertion in Escherichia coli have been studied using only a small set of specific model substrates, it is generally assumed that most secretory proteins and inner membrane proteins use the Sec translocon. Therefore, we have studied the role of the Sec translocon using subproteome analysis of cells depleted of the essential translocon component SecE. The steady-state proteomes and the proteome dynamics were evaluated using one- and two-dimensional gel analysis, followed by mass spectrometry-based protein identification and extensive immunoblotting. The analysis showed that upon SecE depletion (i) secretory proteins aggregated in the cytoplasm and the cytoplasmic sigma(32) stress response was induced, (ii) the accumulation of outer membrane proteins was reduced, with the exception of OmpA, Pal, and FadL, and (iii) the accumulation of a surprisingly large number of inner membrane proteins appeared to be unaffected or increased. These proteins lacked large translocated domains and/or consisted of only one or two transmembrane segments. Our study suggests that several secretory and inner membrane proteins can use Sec translocon-independent pathways or have superior access to the remaining Sec translocons present in SecE-depleted cells.

AB - The Sec translocon is a protein-conducting channel that allows polypeptides to be transferred across or integrated into a membrane. Although protein translocation and insertion in Escherichia coli have been studied using only a small set of specific model substrates, it is generally assumed that most secretory proteins and inner membrane proteins use the Sec translocon. Therefore, we have studied the role of the Sec translocon using subproteome analysis of cells depleted of the essential translocon component SecE. The steady-state proteomes and the proteome dynamics were evaluated using one- and two-dimensional gel analysis, followed by mass spectrometry-based protein identification and extensive immunoblotting. The analysis showed that upon SecE depletion (i) secretory proteins aggregated in the cytoplasm and the cytoplasmic sigma(32) stress response was induced, (ii) the accumulation of outer membrane proteins was reduced, with the exception of OmpA, Pal, and FadL, and (iii) the accumulation of a surprisingly large number of inner membrane proteins appeared to be unaffected or increased. These proteins lacked large translocated domains and/or consisted of only one or two transmembrane segments. Our study suggests that several secretory and inner membrane proteins can use Sec translocon-independent pathways or have superior access to the remaining Sec translocons present in SecE-depleted cells.

KW - Bacterial Outer Membrane Proteins

KW - Cell Membrane

KW - Escherichia coli

KW - Escherichia coli Proteins

KW - Mass Spectrometry

KW - Membrane Transport Proteins

KW - Proteome

KW - Proteomics

KW - SEC Translocation Channels

KW - Journal Article

KW - Research Support, Non-U.S. Gov't

U2 - 10.1128/JB.01631-07

DO - 10.1128/JB.01631-07

M3 - SCORING: Journal article

C2 - 18296516

VL - 190

SP - 3505

EP - 3525

JO - J BACTERIOL

JF - J BACTERIOL

SN - 0021-9193

IS - 10

ER -