Chemistry and Physics Faculty Articles

Title

Allosteric Signaling Is Bidirectional in an Outer-Membrane Transport Protein

Document Type

Article

Publication Date

11-1-2016

Publication Title

Biophysical Journal

ISSN

0006-3495

Volume

111

Issue/No.

9

First Page

1908

Last Page

1918

Abstract

In BtuB, the Escherichia coli TonB-dependent transporter for vitamin B12, substrate binding to the extracellular surface unfolds a conserved energy coupling motif termed the Ton box into the periplasm. This transmembrane signaling event facilitates an interaction between BtuB and the inner-membrane protein TonB. In this study, continuous-wave and pulse electron paramagnetic resonance in a native outer-membrane preparation demonstrate that signaling also occurs from the periplasmic to the extracellular surface in BtuB. The binding of a TonB fragment to the periplasmic interface alters the configuration of the second extracellular loop and partially dissociates a spin-labeled substrate analog. Moreover, mutants in the periplasmic Ton box that are transport-defective alter the binding site for vitamin B12 in BtuB. This work demonstrates that the Ton box and the extracellular substrate binding site are allosterically coupled in BtuB, and that TonB binding may initiate a partial round of transport.

Comments

©2016 Biophysical Society.

Additional Comments

NIH grant #: GM035215; Deutsch Forschungsgemeinschaft grant #: SFB 807

DOI

10.1016/j.bpj.2016.09.038

This document is currently not available here.

Peer Reviewed

Find in your library

Share

COinS