Exbb Cytoplasmic Loop Deletions Cause Immediate, Proton Motive Force-Independent Growth Arrest

Charles M. Bulathsinghala, Bimal Jana, Kristin R. Baker, Kathleen Postle

Research output: Contribution to journalArticle

3 Citations (Scopus)

Abstract

The Escherichia coli TonB system consists of the cytoplasmic membrane proteins TonB, ExbB, and ExbD and multiple outer membrane active transporters for diverse iron siderophores and vitamin B12. The cytoplasmic membrane proteins harvest and transmit the proton motive force (PMF) to outer membrane transporters. This system, which spans the cell envelope, has only one component with a significant cytoplasmic presence, ExbB. Characterization of sequential 10-residue deletions in the ExbB cytoplasmic loop (residues 40 to 129; referred to as Δ10 proteins) revealed that it was required for all TonB-dependent activities, including interaction between the periplasmic domains of TonB and ExbD. Expression of eight out of nine of the Δ10 proteins at chromosomal levels led to immediate, but reversible, growth arrest. Arrest was not due to collapse of the PMF and did not require the presence of ExbD or TonB. All Δ10 proteins that caused growth arrest were dominant for that phenotype. However, several were not dominant for iron transport, indicating that growth arrest was an intrinsic property of the Δ10 variants, whether or not they could associate with wild-type ExbB proteins. The lack of dominance in iron transport also ruled out trivial explanations for growth arrest, such as high-level induction. Taken together, the data suggest that growth arrest reflected a changed interaction between the ExbB cytoplasmic loop and one or more unknown growth-regulatory proteins. Consistent with that, a large proportion of the ExbB cytoplasmic loop between transmembrane domain 1 (TMD1) and TMD2 is predicted to be disordered, suggesting the need for interaction with one or more cytoplasmic proteins to induce a final structure.

Original languageEnglish (US)
Pages (from-to)4580-4591
Number of pages12
JournalJournal of bacteriology
Volume195
Issue number20
DOIs
StatePublished - Oct 18 2013

Fingerprint

Proton-Motive Force
Growth
Proteins
Membrane Transport Proteins
Iron
Membrane Proteins
Cell Membrane
Siderophores
Vitamin B 12
Escherichia coli
Phenotype

All Science Journal Classification (ASJC) codes

  • Microbiology
  • Molecular Biology

Cite this

@article{371f8fa740884356bf416a6301abe709,
title = "Exbb Cytoplasmic Loop Deletions Cause Immediate, Proton Motive Force-Independent Growth Arrest",
abstract = "The Escherichia coli TonB system consists of the cytoplasmic membrane proteins TonB, ExbB, and ExbD and multiple outer membrane active transporters for diverse iron siderophores and vitamin B12. The cytoplasmic membrane proteins harvest and transmit the proton motive force (PMF) to outer membrane transporters. This system, which spans the cell envelope, has only one component with a significant cytoplasmic presence, ExbB. Characterization of sequential 10-residue deletions in the ExbB cytoplasmic loop (residues 40 to 129; referred to as Δ10 proteins) revealed that it was required for all TonB-dependent activities, including interaction between the periplasmic domains of TonB and ExbD. Expression of eight out of nine of the Δ10 proteins at chromosomal levels led to immediate, but reversible, growth arrest. Arrest was not due to collapse of the PMF and did not require the presence of ExbD or TonB. All Δ10 proteins that caused growth arrest were dominant for that phenotype. However, several were not dominant for iron transport, indicating that growth arrest was an intrinsic property of the Δ10 variants, whether or not they could associate with wild-type ExbB proteins. The lack of dominance in iron transport also ruled out trivial explanations for growth arrest, such as high-level induction. Taken together, the data suggest that growth arrest reflected a changed interaction between the ExbB cytoplasmic loop and one or more unknown growth-regulatory proteins. Consistent with that, a large proportion of the ExbB cytoplasmic loop between transmembrane domain 1 (TMD1) and TMD2 is predicted to be disordered, suggesting the need for interaction with one or more cytoplasmic proteins to induce a final structure.",
author = "Bulathsinghala, {Charles M.} and Bimal Jana and Baker, {Kristin R.} and Kathleen Postle",
year = "2013",
month = "10",
day = "18",
doi = "10.1128/JB.00334-13",
language = "English (US)",
volume = "195",
pages = "4580--4591",
journal = "Journal of Bacteriology",
issn = "0021-9193",
publisher = "American Society for Microbiology",
number = "20",

}

Exbb Cytoplasmic Loop Deletions Cause Immediate, Proton Motive Force-Independent Growth Arrest. / Bulathsinghala, Charles M.; Jana, Bimal; Baker, Kristin R.; Postle, Kathleen.

In: Journal of bacteriology, Vol. 195, No. 20, 18.10.2013, p. 4580-4591.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Exbb Cytoplasmic Loop Deletions Cause Immediate, Proton Motive Force-Independent Growth Arrest

AU - Bulathsinghala, Charles M.

AU - Jana, Bimal

AU - Baker, Kristin R.

AU - Postle, Kathleen

PY - 2013/10/18

Y1 - 2013/10/18

N2 - The Escherichia coli TonB system consists of the cytoplasmic membrane proteins TonB, ExbB, and ExbD and multiple outer membrane active transporters for diverse iron siderophores and vitamin B12. The cytoplasmic membrane proteins harvest and transmit the proton motive force (PMF) to outer membrane transporters. This system, which spans the cell envelope, has only one component with a significant cytoplasmic presence, ExbB. Characterization of sequential 10-residue deletions in the ExbB cytoplasmic loop (residues 40 to 129; referred to as Δ10 proteins) revealed that it was required for all TonB-dependent activities, including interaction between the periplasmic domains of TonB and ExbD. Expression of eight out of nine of the Δ10 proteins at chromosomal levels led to immediate, but reversible, growth arrest. Arrest was not due to collapse of the PMF and did not require the presence of ExbD or TonB. All Δ10 proteins that caused growth arrest were dominant for that phenotype. However, several were not dominant for iron transport, indicating that growth arrest was an intrinsic property of the Δ10 variants, whether or not they could associate with wild-type ExbB proteins. The lack of dominance in iron transport also ruled out trivial explanations for growth arrest, such as high-level induction. Taken together, the data suggest that growth arrest reflected a changed interaction between the ExbB cytoplasmic loop and one or more unknown growth-regulatory proteins. Consistent with that, a large proportion of the ExbB cytoplasmic loop between transmembrane domain 1 (TMD1) and TMD2 is predicted to be disordered, suggesting the need for interaction with one or more cytoplasmic proteins to induce a final structure.

AB - The Escherichia coli TonB system consists of the cytoplasmic membrane proteins TonB, ExbB, and ExbD and multiple outer membrane active transporters for diverse iron siderophores and vitamin B12. The cytoplasmic membrane proteins harvest and transmit the proton motive force (PMF) to outer membrane transporters. This system, which spans the cell envelope, has only one component with a significant cytoplasmic presence, ExbB. Characterization of sequential 10-residue deletions in the ExbB cytoplasmic loop (residues 40 to 129; referred to as Δ10 proteins) revealed that it was required for all TonB-dependent activities, including interaction between the periplasmic domains of TonB and ExbD. Expression of eight out of nine of the Δ10 proteins at chromosomal levels led to immediate, but reversible, growth arrest. Arrest was not due to collapse of the PMF and did not require the presence of ExbD or TonB. All Δ10 proteins that caused growth arrest were dominant for that phenotype. However, several were not dominant for iron transport, indicating that growth arrest was an intrinsic property of the Δ10 variants, whether or not they could associate with wild-type ExbB proteins. The lack of dominance in iron transport also ruled out trivial explanations for growth arrest, such as high-level induction. Taken together, the data suggest that growth arrest reflected a changed interaction between the ExbB cytoplasmic loop and one or more unknown growth-regulatory proteins. Consistent with that, a large proportion of the ExbB cytoplasmic loop between transmembrane domain 1 (TMD1) and TMD2 is predicted to be disordered, suggesting the need for interaction with one or more cytoplasmic proteins to induce a final structure.

UR - http://www.scopus.com/inward/record.url?scp=84885467567&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=84885467567&partnerID=8YFLogxK

U2 - 10.1128/JB.00334-13

DO - 10.1128/JB.00334-13

M3 - Article

C2 - 23913327

AN - SCOPUS:84885467567

VL - 195

SP - 4580

EP - 4591

JO - Journal of Bacteriology

JF - Journal of Bacteriology

SN - 0021-9193

IS - 20

ER -