Browse
Submit Data
Databases
API
Help

Dataset Information

14 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

Amino Acid Substitution in the Major Multidrug Efflux Transporter Protein AcrB Contributes to Low Susceptibility to Azithromycin in Haemophilus influenzae.

ABSTRACT: Clarithromycin-resistant Haemophilus influenzae strains with a nonsense mutation in acrR generally exhibited susceptibility to azithromycin, although one strain was found to be nonsusceptible; we aimed to clarify the differences. This strain had an amino acid substitution, Arg327Ser, in AcrB. Introduction of this substitution into H. influenzae Rd caused an increase in the MIC of azithromycin, suggesting that this substitution contributed to nonsusceptibility. These findings indicate that azithromycin-nonsusceptible isolates could occur through stepwise mutation in the acr region.

SUBMITTER: Seyama S

PROVIDER: S-EPMC5655073 | biostudies-literature | 2017 Nov

REPOSITORIES: biostudies-literature

ACCESS DATA

Json Xml

Publications

Amino Acid Substitution in the Major Multidrug Efflux Transporter Protein AcrB Contributes to Low Susceptibility to Azithromycin in Haemophilus influenzae.

Seyama Shoji S Wajima Takeaki T Nakaminami Hidemasa H Noguchi Norihisa N

Antimicrobial agents and chemotherapy 20171024 11

Clarithromycin-resistant Haemophilus influenzae strains with a nonsense mutation in acrR generally exhibited susceptibility to azithromycin, although one strain was found to be nonsusceptible; we aimed to clarify the differences. This strain had an amino acid substitution, Arg327Ser, in AcrB. Introduction of this substitution into H. influenzae Rd caused an increase in the MIC of azithromycin, suggesting that this substitution contributed to nonsusceptibility. These findings ...[more]

PMID: 28848006

Similar Datasets

Phylogenetic and functional characterisation of the Haemophilus influenzae multidrug efflux pump AcrB.

Project description:Multidrug resistance in Gram-negative bacteria can arise by the over-expression of multidrug efflux pumps, which can extrude a wide range of antibiotics. Here we describe the ancestral Haemophilus influenzae efflux pump AcrB (AcrB-Hi). We performed a phylogenetic analysis of hundreds of RND-type transporters. We found that AcrB-Hi is a relatively ancient efflux pump, which nonetheless can export the same range of antibiotics as its evolved colleague from Escherichia coli. AcrB-Hi was not inhibited by the efflux pump inhibitor ABI-PP, and could export bile salts weakly. This points to an environmental adaptation of RND transporters. We also explain the sensitivity of H. influenzae cells to β-lactams and novobiocin by the outer membrane porin OmpP2. This porin counterbalances the AcrB-Hi efflux by leaking the drugs back into the cells. We hypothesise that multidrug recognition by RND-type pumps is not an evolutionarily acquired ability, and has been present since ancient promiscuous transporters.

| S-EPMC6744504 | biostudies-literature

Coarse-grained simulations of conformational changes in the multidrug efflux transporter AcrB.

Project description:The multidrug resistance (MDR) system actively pumps antibiotics out of cells causing serious health problems. During the pumping, AcrB (one of the key components of MDR) undergoes a series of large-scale and proton-motive conformational changes. Capturing the conformational changes through all-atom simulations is challenging. Here, we implement a hybrid coarse-grained force field to investigate the conformational changes of AcrB in the porter domain under different protonation states of Asp407/Asp408 in the trans-membrane domain. Our results show that protonation of Asp408 in monomer III (extrusion) stabilizes the asymmetric structure of AcrB; deprotonation of Asp408 induces clear opening of the entrance and closing of the exit leading to the transition from extrusion to access state. The structural changes in the porter domain of AcrB are strongly coupled with the proton translocation stoichiometry in the trans-membrane domain. Moreover, our simulations support the postulation that AcrB should adopt the symmetric resting state in a substrate-free situation.

| S-EPMC5614849 | biostudies-literature

Substrate-dependent dynamics of the multidrug efflux transporter AcrB of Escherichia coli.

Project description:The resistance-nodulation-cell division (RND)-type xenobiotic efflux system plays a major role in the multidrug resistance of gram-negative bacteria. The only constitutively expressed RND system of Escherichia coli consists of the inner membrane transporter AcrB, the membrane fusion protein AcrA, and the outer membrane channel TolC. The latter two components are shared with another RND-type transporter AcrD, whose expression is induced by environmental stimuli. Here, we demonstrate how RND-type ternary complexes, which span two membranes and the cell wall, form in vivo. Total internal reflection fluorescence (TIRF) microscopy revealed that most fluorescent foci formed by AcrB fused to green fluorescent protein (GFP) were stationary in the presence of TolC but showed lateral displacements when tolC was deleted. The fraction of stationary AcrB-GFP foci decreased with increasing levels of AcrD. We propose that the AcrB-containing complex becomes unstable upon the induction of AcrD, which presumably replaces AcrB, a process we call "transporter exchange." This instability is suppressed by AcrB-specific substrates, suggesting that the ternary complex is stabilised when it is in action. These results suggest that the assembly of the RND-type efflux system is dynamically regulated in response to external stimuli, shedding new light on the adaptive antibiotic resistance of bacteria.

| S-EPMC4768149 | biostudies-literature

Multiple entry pathways within the efflux transporter AcrB contribute to multidrug recognition.

Project description:AcrB is the major multidrug exporter in Escherichia coli. Although several substrate-entrances have been identified, the specificity of these various transport paths remains unclear. Here we present evidence for a substrate channel (channel 3) from the central cavity of the AcrB trimer, which is connected directly to the deep pocket without first passing the switch-loop and the proximal pocket . Planar aromatic cations, such as ethidium, prefer channel 3 to channels 1 and 2. The efflux through channel 3 increases by targeted mutations and is not in competition with the export of drugs such as minocycline and erythromycin through channels 1 and 2. A switch-loop mutant, in which the pathway from the proximal to the deep pocket is hindered, can export only channel 3-utilizing drugs. The usage of multiple entrances thus contributes to the recognition and transport of a wide range of drugs with different physicochemical properties.

| S-EPMC5760665 | biostudies-literature

Crystal structure of the multidrug efflux transporter AcrB at 3.1A resolution reveals the N-terminal region with conserved amino acids.

Project description:Crystal structures of the bacterial multidrug transporter AcrB in R32 and C2 space groups showing both symmetric and asymmetric trimeric assemblies, respectively, supplemented with biochemical investigations, have provided most of the structural basis for a molecular level understanding of the protein structure and mechanisms for substrate uptake and translocation carried out by this 114-kDa inner membrane protein. They suggest that AcrB captures ligands primarily from the periplasm. Substrates can also enter the inner cavity of the transporter from the cytoplasm, but the exact mechanism of this remains undefined. Analysis of the amino acid sequences of AcrB and its homologs revealed the presence of conserved residues at the N-terminus including two phenylalanines which may be exposed to the cytoplasm. Any potential role that these conserved residues may play in function has not been addressed by existing biochemical or structural studies. Since phenylalanine residues elsewhere in the protein have been implicated in ligand binding, we explored the structure of this N-terminal region to investigate structural determinants near the cytoplasmic opening that may mediate drug uptake. Our structure of AcrB in R32 space group reveals an N-terminus loop, reducing the diameter of the central opening to approximately 15 A as opposed to the previously reported value of approximately 30 A for crystal structures in this space group with disordered N-terminus. Recent structures of the AcrB in C2 space group have revealed a helical conformation of this N-terminus but have not discussed its possible implications. We present the crystal structure of AcrB that reveals the structure of the N-terminus containing the conserved residues. We hope that the structural information provides a structural basis for others to design further biochemical investigation of the role of this portion of AcrB in mediating cytoplasmic ligand discrimination and uptake.

| S-EPMC2023878 | biostudies-literature

Substrate binding accelerates the conformational transitions and substrate dissociation in multidrug efflux transporter AcrB.

Project description:The tripartite efflux pump assembly AcrAB-TolC is the major multidrug resistance transporter in E. coli. The inner membrane transporter AcrB is a homotrimer, energized by the proton movement down the transmembrane electrochemical gradient. The asymmetric crystal structures of AcrB with three monomers in distinct conformational states [access (A), binding (B) and extrusion (E)] support a functional rotating mechanism, in which each monomer of AcrB cycles among the three states in a concerted way. However, the relationship between the conformational changes during functional rotation and drug translocation has not been totally understood. Here, we explored the conformational changes of the AcrB homotrimer during the ABE to BEA transition in different substrate-binding states using targeted MD simulations. It was found that the dissociation of substrate from the distal binding pocket of B monomer is closely related to the concerted conformational changes in the translocation pathway, especially the side chain reorientation of Phe628 and Tyr327. A second substrate binding at the proximal binding pocket of A monomer evidently accelerates the conformational transitions as well as substrate dissociation in B monomer. The acceleration effect of the multi-substrate binding mode provides a molecular explanation for the positive cooperativity observed in the kinetic studies of substrate efflux and deepens our understanding of the functional rotating mechanism of AcrB.

| S-EPMC4394701 | biostudies-literature

Molecular Interactions of Carbapenem Antibiotics with the Multidrug Efflux Transporter AcrB of Escherichia coli.

Project description:The drug/proton antiporter AcrB, engine of the major efflux pump AcrAB(Z)-TolC of Escherichia coli and other bacteria, is characterized by its impressive ability to transport chemically diverse compounds, conferring a multi-drug resistance (MDR) phenotype. Although hundreds of small molecules are known to be AcrB substrates, only a few co-crystal structures are available to date. Computational methods have been therefore intensively employed to provide structural and dynamical fingerprints related to transport and inhibition of AcrB. In this work, we performed a systematic computational investigation to study the interaction between representative carbapenem antibiotics and AcrB. We focused on the interaction of carbapenems with the so-called distal pocket, a region known for its importance in binding inhibitors and substrates of AcrB. Our findings reveal how the different physico-chemical nature of these antibiotics is reflected on their binding preference for AcrB. The molecular-level information provided here could help design new antibiotics less susceptible to the efflux mechanism.

| S-EPMC7037162 | biostudies-literature

Switch-loop flexibility affects transport of large drugs by the promiscuous AcrB multidrug efflux transporter.

Project description:Multidrug efflux transporters recognize a variety of structurally unrelated compounds for which the molecular basis is poorly understood. For the resistance nodulation and cell division (RND) inner membrane component AcrB of the AcrAB-TolC multidrug efflux system from Escherichia coli, drug binding occurs at the access and deep binding pockets. These two binding areas are separated by an 11-amino-acid-residue-containing switch loop whose conformational flexibility is speculated to be essential for drug binding and transport. A G616N substitution in the switch loop has a distinct and local effect on the orientation of the loop and on the ability to transport larger drugs. Here, we report a distinct phenotypical pattern of drug recognition and transport for the G616N variant, indicating that drug substrates with minimal projection areas of >70 Å(2) are less well transported than other substrates.

| S-EPMC4136034 | biostudies-literature

Vestibules are part of the substrate path in the multidrug efflux transporter AcrB of Escherichia coli.

Project description:The path of substrates in the multidrug efflux pump AcrB of Escherichia coli was examined by using labeling with a lipophilic substrate mimic, Bodipy FL maleimide. Four (out of eight) residues in the vestibule bound the dye, suggesting its role in substrate transport, whereas only one (out of nine) residue in the central cavity tested positive.

| S-EPMC3187200 | biostudies-literature

Novel sialic acid transporter of Haemophilus influenzae.

Project description:Nontypeable Haemophilus influenzae is an opportunistic pathogen and a common cause of otitis media in children and of chronic bronchitis and pneumonia in patients with chronic obstructive pulmonary disease. The lipooligosaccharides, a major component of the outer membrane of H. influenzae, play an important role in microbial virulence and pathogenicity. N-Acetylneuraminic acid (sialic acid) can be incorporated into the lipooligosaccharides as a terminal nonreducing sugar. Although much of the pathway of sialic acid incorporation into lipooligosaccharides is understood, the transporter responsible for N-acetylneuraminic acid uptake in H. influenzae has yet to be characterized. In this paper we demonstrate that this transporter is a novel sugar transporter of the tripartite ATP-independent periplasmic transporter family. In the absence of this transporter, H. influenzae cannot incorporate sialic acid into its lipooligosaccharides, making the organism unable to survive when exposed to human serum and causing reduced viability in biofilm growth.

| S-EPMC1231074 | biostudies-literature

OmicsDI is part of the ELIXIR infrastructure

OmicsDI is an Elixir interoperability service. Learn more ›

OmicsDI Databases

PRIDE
PeptideAtlas
MassIVE
JPOST Repository
Physiome Model Repository

EGA
EVA
ENA
LINCS
PAXDB
Cell Collective

MetaboLights
Metabolomics Workbench
MetabolomeExpress
GNPS
BioModels
FAIRDOMHub

ArrayExpress
dbGaP
ExpressionAtlas
GEO
NODE

Information

Databases
Help
API
Contact us
Code on GitHub
Terms of use
Submit Data