Native Cell Environment Constrains Loop Structure in the Escherichia coli Cobalamin Transporter BtuB.

ABSTRACT: The extracellular loops of bacterial outer membrane (OM) transporters are thought to sample a range of conformations in the apo state but to undergo a gating motion and assume a more defined conformation upon the binding of substrate. Here, we use pulse electron paramagnetic resonance to examine the conformations of the extracellular loops of BtuB, the Escherichia coli TonB-dependent vitamin B₁₂ transporter, in whole cells. Unlike previous measurements carried out in vitro, the loops assume well-defined configurations in situ that closely match the in surfo crystal structures. Moreover, there is no evidence that the loops undergo significant gating motions upon the binding of substrate. The results demonstrate that the structure of BtuB is dependent upon an intact native OM envi

SUBMITTER: Nyenhuis DA 

PROVIDER: S-EPMC7642247 | biostudies-literature | 2020 Oct

REPOSITORIES: biostudies-literature