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Publication Abstract from PubMed

beta-barrel outer membrane proteins (Omps) are key functional components of the outer membranes of Gram-negative bacteria, mitochondria, and plastids. In bacteria, their biogenesis requires the beta-barrel-assembly machinery (Bam) with the central insertase BamA, but the exact translocation and insertion mechanism remains elusive. The BamA insertase features a loosely closed gating region between the first and last beta-strand 16. Here, we describe approximately 70% complete sequence-specific NMR resonance assignments of the transmembrane region of the BamA beta-barrel in detergent micelles. On the basis of the assignments, NMR spectra show that the BamA barrel populates a conformational ensemble in slow exchange equilibrium, both in detergent micelles and lipid bilayer nanodiscs. Individual conformers can be selected from the ensemble by the introduction of a C-terminal strand extension, single-point mutations, or specific disulfide cross-linkings, and these modifications at the barrel seam are found to be allosterically coupled to sites at the entire barrel circumference. The resonance assignment provides a platform for mechanistic studies of BamA at atomic resolution, as well as for investigating interactions with potential antibiotic drugs and partner proteins.

Sequence-Specific Solution NMR Assignments of the beta-Barrel Insertase BamA to Monitor Its Conformational Ensemble at the Atomic Level.,Hartmann JB, Zahn M, Burmann IM, Bibow S, Hiller S J Am Chem Soc. 2018 Sep 12;140(36):11252-11260. doi: 10.1021/jacs.8b03220. Epub, 2018 Sep 4. PMID:30125090^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.