Substrate-dependent unfolding of the energy coupling motif of a membrane transport protein determined by double electron-electron resonance.

ABSTRACT: BtuB is a TonB-dependent transport protein that binds and carries vitamin B(12) across the outer membrane of Gram negative bacteria such as Escherichia coli. Previous work has demonstrated that the Ton box, a highly conserved segment near the N-terminus of the protein, undergoes an order-to-disorder transition upon the binding of substrate. Here, we incorporate pairs of nitroxide spin labels into membrane reconstituted BtuB and utilize a four-pulse double electron-electron resonance (DEER) experiment to measure distances between the Ton box and the periplasmic surface of the transporter with and without substrate. During reconstitution, the labeled membrane protein was diluted with wild-type protein, which significantly reduced the intermolecular electron spin-spin relaxation rate and incr

SUBMITTER: Xu Q 

PROVIDER: S-EPMC2515220 | biostudies-literature | 2006 Sep

REPOSITORIES: biostudies-literature