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Contents

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. [2] OMPs are synthesized in cytoplasm and transported to the periplasm by Sec translocon.[3] With in the periplasm, chaperones (SurA, Skp, and DegP) guide the OMPs to the BAM complex.[4] BAM complex function by folding and inserting the new OMPs into the outer membrane. Here , while non-essential, plays an important role in the assembly of OMPs by interacting with the BamA polypeptide transport-associated(POTRA regions). [5] BamA contains an N-terminal periplasmic domain with five polypeptide transport-associated (POTRA) repeats in addition to the outer membrane-embedded C-terminal β-barrel domain.[6] 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

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Overview

The native E. coli BamB structure contains residues 21–392 arranged as an eight bladed with hole at the center.[7] 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. [8] This help the BamB to interact with the BamA. The interacting residues are found in these loops.

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).[9] 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. [10] 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. The c terminus signature sequences i.e. Phe of SurA is responsible for recognition by BamA. This facilitates the delivery, folding and insertion of OMPs into the outer membrane. [11]

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 around this region. The R195 of IL4 is responsible for the salt bridge formation with the D241 of PORTA 3 region of BamA protein.[12]


Additional Information

 3Q7N
 3Q7O


References

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  1. ↑ 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
  2. ↑ Ishii K, Nakazawa K, Tadokoro K, Ikeda T, Takamatsu T, Watanabe J, Yoda K, Matsubayashi T, Sakai F, Suzuki S. [Dynamic local cerebral circulation study in patients with cerebral diseases--using 99mTc-HSA-D mainly compared with 99mTc-HSA]. Kaku Igaku. 1989 Jan;26(1):35-44. PMID:2724633
  3. ↑ Amann VL, Lerch RA, Anderson K, Wertz GW. Bovine respiratory syncytial virus nucleocapsid protein: mRNA sequence analysis and expression from recombinant vaccinia virus vectors. J Gen Virol. 1992 Apr;73 ( Pt 4):999-1003. PMID:1634882
  4. ↑ Amann VL, Lerch RA, Anderson K, Wertz GW. Bovine respiratory syncytial virus nucleocapsid protein: mRNA sequence analysis and expression from recombinant vaccinia virus vectors. J Gen Virol. 1992 Apr;73 ( Pt 4):999-1003. PMID:1634882
  5. ↑ Monsur KA, Begum YA, Ahmed ZU, Rahman S. Evidence of multiple infections in cases of diarrhea due to enterotoxigenic Escherichia coli. J Infect Dis. 1989 Jan;159(1):144-5. PMID:2642521
  6. ↑ Matsushima T, Maekubo H, Yoshida T, Taneda H, Yoshida J, Miyazaki T, Okada F. Deranged metabolism of cyclic nucleotides in liver diseases. Horm Metab Res. 1985 Jun;17(6):306-7. PMID:2991101 doi:http://dx.doi.org/10.1055/s-2007-1013525
  7. ↑ 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
  8. ↑ Matsushima T, Maekubo H, Yoshida T, Taneda H, Yoshida J, Miyazaki T, Okada F. Deranged metabolism of cyclic nucleotides in liver diseases. Horm Metab Res. 1985 Jun;17(6):306-7. PMID:2991101 doi:http://dx.doi.org/10.1055/s-2007-1013525
  9. ↑ 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
  10. ↑ Monsur KA, Begum YA, Ahmed ZU, Rahman S. Evidence of multiple infections in cases of diarrhea due to enterotoxigenic Escherichia coli. J Infect Dis. 1989 Jan;159(1):144-5. PMID:2642521
  11. ↑ Amann VL, Lerch RA, Anderson K, Wertz GW. Bovine respiratory syncytial virus nucleocapsid protein: mRNA sequence analysis and expression from recombinant vaccinia virus vectors. J Gen Virol. 1992 Apr;73 ( Pt 4):999-1003. PMID:1634882
  12. ↑ 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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