Dataset Information

Structural and functional insights into the role of BamD and BamE within the ?-barrel assembly machinery in Neisseria gonorrhoeae.

ABSTRACT: The ?-barrel assembly machinery (BAM) is a conserved multicomponent protein complex responsible for the biogenesis of ?-barrel outer membrane proteins (OMPs) in Gram-negative bacteria. Given its role in the production of OMPs for survival and pathogenesis, BAM represents an attractive target for the development of therapeutic interventions, including drugs and vaccines against multidrug-resistant bacteria such as Neisseria gonorrhoeae The first structure of BamA, the central component of BAM, was from N. gonorrhoeae, the etiological agent of the sexually transmitted disease gonorrhea. To aid in pharmaceutical targeting of BAM, we expanded our studies to BamD and BamE within BAM of this clinically relevant human pathogen. We found that the presence of BamD, but not BamE, is essential for gonococcal viability. However, BamE, but not BamD, was cell-surface-displayed under native conditions; however, in the absence of BamE, BamD indeed becomes surface-exposed. Loss of BamE altered cell envelope composition, leading to slower growth and an increase in both antibiotic susceptibility and formation of membrane vesicles containing greater amounts of vaccine antigens. Both BamD and BamE are expressed in diverse gonococcal isolates, under host-relevant conditions, and throughout different phases of growth. The solved structures of Neisseria BamD and BamE share overall folds with Escherichia coli proteins but contain differences that may be important for function. Together, these studies highlight that, although BAM is conserved across Gram-negative bacteria, structural and functional differences do exist across species, which may be leveraged in the development of species-specific therapeutics in the effort to combat multidrug resistance.

SUBMITTER: Sikora AE

PROVIDER: S-EPMC5787791 | biostudies-literature | 2018 Jan

REPOSITORIES: biostudies-literature

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Structural and functional insights into the role of BamD and BamE within the β-barrel assembly machinery in <i>Neisseria gonorrhoeae</i>.

Sikora Aleksandra E AE Wierzbicki Igor H IH Zielke Ryszard A RA Ryner Rachael F RF Korotkov Konstantin V KV Buchanan Susan K SK Noinaj Nicholas N

The Journal of biological chemistry 20171211 4

The β-barrel assembly machinery (BAM) is a conserved multicomponent protein complex responsible for the biogenesis of β-barrel outer membrane proteins (OMPs) in Gram-negative bacteria. Given its role in the production of OMPs for survival and pathogenesis, BAM represents an attractive target for the development of therapeutic interventions, including drugs and vaccines against multidrug-resistant bacteria such as <i>Neisseria gonorrhoeae</i> The first structure of BamA, the central component of ...[more]

PMID: 29229778

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Project description:Most integral outer membrane proteins (OMPs) of Gram-negative bacteria, such as Escherichia coli, assume a β-barrel structure. The β-barrel assembly machine (Bam), a five-member complex composed of β-barrel OMP BamA and four associated lipoproteins, BamB, BamC, BamD, and BamE, folds and inserts OMPs into the outer membrane. The two essential proteins BamA and BamD interact to stabilize two subcomplexes, BamAB and BamCDE, and genetic and structural evidence suggests that interactions between BamA and BamD occur via an electrostatic interaction between a conserved aspartate residue in a periplasmic domain of BamA and a conserved arginine in BamD. In this work, we characterize charge-change mutations at these key BamA and BamD residues and nearby charged residues in BamA with respect to OMP assembly and Bam complex stability. We show that Bam complex stability does not correlate with function, that BamA and BamD must adopt at least two active conformational states during OMP assembly, and that these charged residues are not required for function. Rather, these charged residues are important for coordinating the activities of BamA and BamD to allow efficient OMP assembly. We present a model of OMP assembly wherein recognition and binding of unfolded OMP substrate by BamA and BamD induce a signaling interaction between the two proteins, causing conformational changes necessary for the assembly reaction to proceed. By analogy to signal sequence recognition by SecYEG, we believe these BamA-BamD interactions ensure that both substrate and complex are competent for OMP assembly before the assembly reaction commences.IMPORTANCE Conformational changes in the proteins of the β-barrel assembly machine (Bam complex) are associated with the folding and assembly of outer membrane proteins (OMPs) in Gram-negative bacteria. We show that electrostatic interactions between the two essential proteins BamA and BamD coordinate conformational changes upon binding of unfolded substrate that allow the assembly reaction to proceed. Mutations affecting this interaction are lethal not because they destabilize the Bam complex but rather because they disrupt this coordination. Our model of BamA-BamD interactions regulating conformation in response to proper substrate interaction is reminiscent of conformational changes the secretory (Sec) machinery undergoes after signal sequence recognition that ensure protein quality control.

Dataset Information

Structural and functional insights into the role of BamD and BamE within the ?-barrel assembly machinery in Neisseria gonorrhoeae.

Publications

Structural and functional insights into the role of BamD and BamE within the β-barrel assembly machinery in <i>Neisseria gonorrhoeae</i>.

Similar Datasets

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