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1 Introduction
2 Structure
3 Additional Information
4 References

Introduction

BamB (PDB entry:3Q7M)is one of the lipoprotein found in the β-barrel assembly machinery (BAM) complex in outer membrane of Escherichia coli. The E. coli BAM complex consists of five subunits named BamA (88 kDa), BamB (40 kDa), BamC (34 kDa), BamD (26 kDa) and BamE (10 kDa).^[1] The outer membrane contains numerous β-barrel proteins commonly called outer membrane proteins (OMPs), which serve as in cargo transport and signaling and are also vital for membrane biogenesis. OMPs are synthesized in cytoplasm and transported to the periplasm by Sec translocon. With in the periplasm, chaperones (SurA, Skp, and DegP) guide the OMPs to the BAM complex. BAM complex function by folding and inserting the new OMPs into the outer membrane. Here BamB, while non-essential, plays an important role in the assembly of OMPs by interacting with the BamA polypeptide transport-associated(POTRA regions). Thus BamB act as a scaffold to optimally orient POTRA regions for interaction with other BAM components, chaperones, and nascent OMPs. BamB is not essential for the bacteria because it can survive without it but it is noticed also now that BamB is essential for folding efficiency of OMPs.

Structure

1 Overview
2 Interactions with other molecules
3 Active site organisation
4 Conclusions

Overview

The native E. coli BamB structure contains residues 21–392 arranged as an eight bladed with hole at the center. Each blade is connected by interconnected loop (IL). BamB is strongly electronegative at the center at either side of the hole due to the presence of strong residues in these regions (E197, D246, D248, D288, D303, E370). Among the ILs, IL4 and IL5 are either partially or completely disordered. This helps the BamB to interact with the BamA. Moreover, the interacting residues are found in these loops. How the overall structure looks like? Subunits orientation, chains: the number and relative positions, etc. Here is the of the main chain of lysozyme. And here is the of the same lysozyme molecule.

Interactions with other molecules

BamB interact with BamA through residues[[1]] (L192, L194, R195, D246, and D248). These residues are found on IL4 [[2]]( L192, L194, R195) and IL5 (D246, D248). BamB interacts with the PORTA 2-4 regions of BamA. The IL4 of the BamB (R195)protein interact with the PORTA 3 regions of the BamA(D241)region by forming a salt bridge. BamB coordinates or optimally arranged the PORTA domains for nascent OMP recognition and insertion.BamB form a triple complex: BamB-BamA-SurA and mediate the interaction between BamA and SurA. This facilitates the delivery, folding and insertion of OMPs into the outer membrane. interact with the Close up picture, with explanation what we see

Active site organisation

The active site of BamB are found in . Both electronegative (E197, D246, D248, D288, D303, E370) and interactive residues of IL4 and IL5 (L192, L194, R195,D246 and D248) are found at the hole / center of the beta barrel region. This region is electronegative due to its electronegative residues around this region. The R195 of IL4 is responsible for the salt bridge formation with the D241 of PORTA 3 region of BamA protein.

Conclusions

Additional Information

References

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↑ Noinaj N, Fairman JW, Buchanan SK. The Crystal Structure of BamB Suggests Interactions with BamA and Its Role within the BAM Complex. J Mol Biol. 2011 Jan 26. PMID:21277859 doi:10.1016/j.jmb.2011.01.042

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Sandbox Reserved 940

From Proteopedia

Contents

Introduction

Structure

Contents

Overview

Interactions with other molecules

Active site organisation

Conclusions

Additional Information

References

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