The role of BamA in outer membrane protein biogenesis in Gram-negative bacteria

Wednesday, October 10, 2012 — Poster Session II
Noon – 2:00 p.m	Natcher Conference Center, Building 45	NIDDK	STRUCTBIO-5

* FARE Award Winner

Authors

• N. Noinaj
• P. Lukacik
• N. Easley
• H. Chang
• T. Lithgow
• S.K. Buchanan

Abstract

Membrane proteins serve essential functions in both bacterial and mammalian cells making them important therapeutic targets. While the mechanism for membrane integration has been well established for alpha-helical membrane proteins, the mechanism for insertion of beta-barrel membrane proteins remains elusive. For Gram-negative bacteria, a complex called the beta-barrel assembly machinery (BAM) complex, consisting of BamA (a beta-barrel membrane protein itself) and four lipoproteins called BamB, BamC, BamD, and BamE, is required for membrane integration. Work from several labs, including ours, has led to the 3D structures of all the components of the BAM complex except for full length BamA, however, they have failed to lead to a plausible mechanism for membrane integration, suggesting that the structure of BamA is likely required in order to understand this unique mechanism. To this end, we have determined the crystal structures of two BamA homologs, including a full length structure which contains a beta-barrel domain consisting of 16-strands with a large periplasmic domain sitting in close proximity to the periplasmic face of the beta-barrel domain. In addition, extracellular loop-6 was found within the beta-barrel domain and could potentially interact with nascent beta-barrel proteins or even other Bam proteins during folding and insertion.

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