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BamA β6C strand and periplasmic turns are critical for outer membrane protein insertion and assembly

DOI: 10.1042/BCJ20170636 DOI Help

Authors: Yinghong Gu (University of East Anglia) , Yi Zeng (University of East Anglia) , Zhongshan Wang (University of East Anglia; Xuzhou Medical University; Sichuan University) , Changjiang Dong (University of East Anglia)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Biochemical Journal

State: Published (Approved)
Published: October 2017
Diamond Proposal Number(s): 9475

Abstract: Outer membrane β-barrel proteins play important roles in importing nutrients, exporting wastes and conducting signals in Gram-negative bacteria, mitochondria and chloroplasts. The outer membrane proteins are inserted and assembled into the outer membrane by OMP85 family proteins. In Escherichia coli , the b-barrel assembly machinery (BAM) contains four lipoproteins BamB, BamC, BamD and BamE, and one outer membrane protein BamA, forming a "top hat"-like structure. Structural and functional studies of the E. coli BAM machinery have revealed that the rotation of periplasmic ring may trigger the barrel b1C-b6C scissor-like movement that promote the unfolded outer membrane protein insertion without using ATP. Here we report the BamA C-terminal barrel structure of Salmonella enterica Typhimurium str. LT2 and functional assays, which reveal that the BamA's C-terminal residue Trp, the b16C strand of the barrel and the periplasmic turns are critical for the functionality of BamA. These findings indicate that the unique b16C and the periplasmic turns of BamA are important for the out membrane insertion and assembly. The periplasmic turns might mediate the rotation of the periplasmic ring to the scissor-like movement of BamA b1C-b6C, triggering the outer membrane protein insertion. These results are important for understanding the outer membrane protein insertion in Gram-negative bacteria, as well as in mitochondria and chloroplasts.

Subject Areas: Biology and Bio-materials


Instruments: I04-1-Macromolecular Crystallography (fixed wavelength)

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