Improper Coordination of BamA and BamD Results in Bam Complex Jamming by a Lipoprotein Substrate

ABSTRACT The β-barrel assembly machinery, the Bam complex, is central to the biogenesis of integral outer membrane proteins (OMPs) as well as OMP-dependent surface-exposed lipoproteins, such as regulator of capsule synthesis protein F (RcsF). Previous genetic analysis established the model that none...

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Autores principales:	Muralidhar Tata, Anna Konovalova
Formato:	article
Lenguaje:	EN
Publicado:	American Society for Microbiology 2019
Materias:	Gram-negative envelope biogenesis Rcs phosphorelay surface-exposed lipoproteins Microbiology QR1-502
Acceso en línea:	https://doaj.org/article/3ba8b16f2e6e46ac8fca4cafb4d20c6f
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spelling	oai:doaj.org-article:3ba8b16f2e6e46ac8fca4cafb4d20c6f2021-11-15T15:55:24ZImproper Coordination of BamA and BamD Results in Bam Complex Jamming by a Lipoprotein Substrate10.1128/mBio.00660-192150-7511https://doaj.org/article/3ba8b16f2e6e46ac8fca4cafb4d20c6f2019-06-01T00:00:00Zhttps://journals.asm.org/doi/10.1128/mBio.00660-19https://doaj.org/toc/2150-7511ABSTRACT The β-barrel assembly machinery, the Bam complex, is central to the biogenesis of integral outer membrane proteins (OMPs) as well as OMP-dependent surface-exposed lipoproteins, such as regulator of capsule synthesis protein F (RcsF). Previous genetic analysis established the model that nonessential components BamE and BamB have overlapping, redundant functions to enhance the kinetics of the highly conserved BamA/BamD core. Here we report that BamE plays a specialized nonredundant role in the Bam complex required for surface exposure of RcsF. We show that the lack of bamE, but not bamB, completely abolishes assembly of RcsF/OMP complexes and establish that the inability to assemble RcsF/OMP complexes is a molecular reason underlying all synthetic lethal interactions of ΔbamE. Our genetic analysis and biochemical cross-linking suggest that RcsF accumulates on BamA when BamA cannot engage with BamD because of its limited availability or the incompatible conformation. The role of BamE is to promote proper coordination of RcsF-bound BamA with BamD to complete OMP assembly around RcsF. We show that in the absence of BamE, RcsF is stalled on BamA, thus blocking its function, and we identify the lipoprotein RcsF as a bona fide jamming substrate of the Bam complex. IMPORTANCE The β-barrel assembly machinery, the Bam complex, consists of five components, BamA to -E, among which BamA and BamD are highly conserved and essential. The nonessential components are believed to play redundant roles simply by improving the rate of β-barrel folding. Here we show that BamE contributes a specific and nonoverlapping function to the Bam complex. BamE coordinates BamA and BamD to form a complex between the lipoprotein RcsF and its partner outer membrane β-barrel protein, allowing RcsF to reach the cell surface. In the absence of BamE, RcsF accumulates on BamA, thus blocking the activity of the Bam complex. As the Bam complex is a major antibiotic target in Gram-negative bacteria, the discovery that a lipoprotein can act as a jamming substrate may open the door for development of novel Bam complex inhibitors.Muralidhar TataAnna KonovalovaAmerican Society for MicrobiologyarticleGram-negative envelope biogenesisRcs phosphorelaysurface-exposed lipoproteinsMicrobiologyQR1-502ENmBio, Vol 10, Iss 3 (2019)
institution	DOAJ
collection	DOAJ
language	EN
topic	Gram-negative envelope biogenesis Rcs phosphorelay surface-exposed lipoproteins Microbiology QR1-502
spellingShingle	Gram-negative envelope biogenesis Rcs phosphorelay surface-exposed lipoproteins Microbiology QR1-502 Muralidhar Tata Anna Konovalova Improper Coordination of BamA and BamD Results in Bam Complex Jamming by a Lipoprotein Substrate
description	ABSTRACT The β-barrel assembly machinery, the Bam complex, is central to the biogenesis of integral outer membrane proteins (OMPs) as well as OMP-dependent surface-exposed lipoproteins, such as regulator of capsule synthesis protein F (RcsF). Previous genetic analysis established the model that nonessential components BamE and BamB have overlapping, redundant functions to enhance the kinetics of the highly conserved BamA/BamD core. Here we report that BamE plays a specialized nonredundant role in the Bam complex required for surface exposure of RcsF. We show that the lack of bamE, but not bamB, completely abolishes assembly of RcsF/OMP complexes and establish that the inability to assemble RcsF/OMP complexes is a molecular reason underlying all synthetic lethal interactions of ΔbamE. Our genetic analysis and biochemical cross-linking suggest that RcsF accumulates on BamA when BamA cannot engage with BamD because of its limited availability or the incompatible conformation. The role of BamE is to promote proper coordination of RcsF-bound BamA with BamD to complete OMP assembly around RcsF. We show that in the absence of BamE, RcsF is stalled on BamA, thus blocking its function, and we identify the lipoprotein RcsF as a bona fide jamming substrate of the Bam complex. IMPORTANCE The β-barrel assembly machinery, the Bam complex, consists of five components, BamA to -E, among which BamA and BamD are highly conserved and essential. The nonessential components are believed to play redundant roles simply by improving the rate of β-barrel folding. Here we show that BamE contributes a specific and nonoverlapping function to the Bam complex. BamE coordinates BamA and BamD to form a complex between the lipoprotein RcsF and its partner outer membrane β-barrel protein, allowing RcsF to reach the cell surface. In the absence of BamE, RcsF accumulates on BamA, thus blocking the activity of the Bam complex. As the Bam complex is a major antibiotic target in Gram-negative bacteria, the discovery that a lipoprotein can act as a jamming substrate may open the door for development of novel Bam complex inhibitors.
format	article
author	Muralidhar Tata Anna Konovalova
author_facet	Muralidhar Tata Anna Konovalova
author_sort	Muralidhar Tata
title	Improper Coordination of BamA and BamD Results in Bam Complex Jamming by a Lipoprotein Substrate
title_short	Improper Coordination of BamA and BamD Results in Bam Complex Jamming by a Lipoprotein Substrate
title_full	Improper Coordination of BamA and BamD Results in Bam Complex Jamming by a Lipoprotein Substrate
title_fullStr	Improper Coordination of BamA and BamD Results in Bam Complex Jamming by a Lipoprotein Substrate
title_full_unstemmed	Improper Coordination of BamA and BamD Results in Bam Complex Jamming by a Lipoprotein Substrate
title_sort	improper coordination of bama and bamd results in bam complex jamming by a lipoprotein substrate
publisher	American Society for Microbiology
publishDate	2019
url	https://doaj.org/article/3ba8b16f2e6e46ac8fca4cafb4d20c6f
work_keys_str_mv	AT muralidhartata impropercoordinationofbamaandbamdresultsinbamcomplexjammingbyalipoproteinsubstrate AT annakonovalova impropercoordinationofbamaandbamdresultsinbamcomplexjammingbyalipoproteinsubstrate
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Improper Coordination of BamA and BamD Results in Bam Complex Jamming by a Lipoprotein Substrate

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