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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 ?10 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 ?10 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 ?10 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 ?10 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.

SUBMITTER: Bulathsinghala CM

PROVIDER: S-EPMC3807443 | biostudies-literature | 2013 Oct

REPOSITORIES: biostudies-literature

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ExbB cytoplasmic loop deletions cause immediate, proton motive force-independent growth arrest.

Bulathsinghala Charles M CM Jana Bimal B Baker Kristin R KR Postle Kathleen K

Journal of bacteriology 20130802 20

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 cytoplasmi ...[more]

PMID: 23913327

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ExbB cytoplasmic loop deletions cause immediate, proton motive force-independent growth arrest.

Publications

ExbB cytoplasmic loop deletions cause immediate, proton motive force-independent growth arrest.

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