Triclosan Resistance in Francisella tularensis: A Site-Directed Mutagenesis Study of the FabI Enzyme

2015 ◽  
Vol 8 (1) ◽  
Author(s):  
N. Silas ◽  
R. Demissie ◽  
L.W.M. Fung
Keyword(s):  
Fatty Acid ◽  
Francisella Tularensis ◽  
Bacterial Resistance ◽  
Fatty Acid Biosynthesis ◽  
Acyl Carrier Protein ◽  
Enzymatic Reaction ◽  
Site Directed Mutagenesis ◽  
E Coli ◽  
Bacterial Fatty Acid ◽  
Triclosan Resistance

An NADH-dependent enoyl-acyl carrier protein reductase, FabI, catalyzes the final step of bacterial fatty acid biosynthesis, reducing the double bond of trans-2-enoyl-ACP to a single bond forming acyl-ACP. Given its importance in bacterial fatty acid synthesis, FabI has become a recognized drug target. Triclosan, a diphenyl ether, targets the FabI, inhibits its activity, and stops bacterial growth. However, as a consequence of triclosan's popularity, and thus its overuse, bacterial resistance to triclosan has been reported. The mutation G93V in Escherichia coli (E. coli) FabI allows E. coli to resist the action of triclosan. We have identified the equivalent residue of G93 in Francisella tularensis FabI (ftFabI) as A92, and prepared a mutant A92V. E. coli cells, transformed with a plasmid containing the ftFabI-A92V gene, were grown, and the gene was overexpressed. From two growths (6 G of cells), 62 mG of protein, with a histidine tag, at a purity of 85% were obtained. Enzymatic activity was assayed by monitoring the absorbance of NADH at 340 nm. In the presence of triclosan, the wild-type protein was almost completely inhibited after NADH was converted to NAD$^+$ in the enzymatic reaction; however the A92V mutant exhibited similar activity with and without triclosan, demonstrating that triclosan resistance may also develop in Francisella tularensis.

scholarly journals β-Ketoacyl-Acyl Carrier Protein Synthase III (FabH) Is a Determining Factor in Branched-Chain Fatty Acid Biosynthesis

2000 ◽  
Vol 182 (2) ◽  
pp. 365-370 ◽  
Author(s):  
Keum-Hwa Choi ◽  
Richard J. Heath ◽  
Charles O. Rock
Keyword(s):  
Fatty Acid ◽  
Fatty Acid Synthase ◽  
Fatty Acid Biosynthesis ◽  
Acyl Carrier Protein ◽  
Chain Fatty Acid ◽  
Carrier Protein ◽  
Acid Biosynthesis ◽  
Biochemical Basis ◽  
E Coli ◽  
Branched Chain

ABSTRACT A universal set of genes encodes the components of the dissociated, type II, fatty acid synthase system that is responsible for producing the multitude of fatty acid structures found in bacterial membranes. We examined the biochemical basis for the production of branched-chain fatty acids by gram-positive bacteria. Two genes that were predicted to encode homologs of the β-ketoacyl-acyl carrier protein synthase III of Escherichia coli (eFabH) were identified in theBacillus subtilis genome. Their protein products were expressed, purified, and biochemically characterized. Both B. subtilis FabH homologs, bFabH1 and bFabH2, carried out the initial condensation reaction of fatty acid biosynthesis with acetyl-coenzyme A (acetyl-CoA) as a primer, although they possessed lower specific activities than eFabH. bFabH1 and bFabH2 also utilized iso- and anteiso-branched-chain acyl-CoA primers as substrates. eFabH was not able to accept these CoA thioesters. Reconstitution of a complete round of fatty acid synthesis in vitro with purified E. coli proteins showed that eFabH was the only E. colienzyme incapable of using branched-chain substrates. Expression of either bFabH1 or bFabH2 in E. coli resulted in the appearance of a branched-chain 17-carbon fatty acid. Thus, the substrate specificity of FabH is an important determinant of branched-chain fatty acid production.

scholarly journals Elucidation of transient protein-protein interactions within carrier protein-dependent biosynthesis

2020 ◽  
Author(s):  
Michael Burkart ◽  
Thomas Bartholow ◽  
Terra Sztain ◽  
Ashay Patel ◽  
D Lee ◽  
...  
Keyword(s):  
Fatty Acid ◽  
Protein Interactions ◽  
Fatty Acid Biosynthesis ◽  
De Novo ◽  
Acyl Carrier Protein ◽  
Protein Docking ◽  
Carrier Protein ◽  
Protein Protein Interactions ◽  
Acid Biosynthesis ◽  
E Coli

Abstract Fatty acid biosynthesis (FAB) is an essential and highly conserved metabolic pathway. In bacteria, this process is mediated by an elaborate network of protein•protein interactions (PPIs) involving a small, dynamic acyl carrier protein that interacts with dozens of other partner proteins (PPs). These PPIs have remained poorly characterized due to their dynamic and transient nature. Using a combination of solution-phase NMR spectroscopy and protein-protein docking simulations, we report a comprehensive residue-by-residue comparison of the PPIs formed during FAB in Escherichia coli. This work reveals the molecular basis of six discrete binding events responsible for E. coli FAB and offers insights into a method to characterize these events and those in related carrier protein-dependent pathways. ONE SENTENCE SUMMARY: Through a combination of structural and computational analysis, a comparative evaluation of protein-protein interactions in de novo fatty acid biosynthesis in E. coli is performed.

scholarly journals The Structure of (3R)-Hydroxyacyl-Acyl Carrier Protein Dehydratase (FabZ) fromPseudomonas aeruginosa

2004 ◽  
Vol 279 (50) ◽  
pp. 52593-52602 ◽  
Author(s):  
Matthew S. Kimber ◽  
Fernando Martin ◽  
Yingjie Lu ◽  
Simon Houston ◽  
Masoud Vedadi ◽  
...  
Keyword(s):  
Fatty Acid ◽  
Fatty Acid Biosynthesis ◽  
Acyl Carrier Protein ◽  
Site Directed Mutagenesis ◽  
Isomerization Reaction ◽  
Antibacterial Drug ◽  
Carrier Protein ◽  
Type Ii ◽  
Active Site Residues ◽  
Acid Biosynthesis

Type II fatty acid biosynthesis systems are essential for membrane formation in bacteria, making the constituent proteins of this pathway attractive targets for antibacterial drug discovery. The third step in the elongation cycle of the type II fatty acid biosynthesis is catalyzed by β-hydroxyacyl-(acyl carrier protein) (ACP) dehydratase. There are two isoforms. FabZ, which catalyzes the dehydration of (3R)-hydroxyacyl-ACP totrans-2-acyl-ACP, is a universally expressed component of the bacterial type II system. FabA, the second isoform, as has more limited distribution in nature and, in addition to dehydration, also carries out the isomerization oftrans-2- tocis-3-decenoyl-ACP as an essential step in unsaturated fatty acid biosynthesis. We report the structure of FabZ from the important human pathogenPseudomonas aeruginosaat 2.5 Å of resolution.PaFabZ is a hexamer (trimer of dimers) with the His/Glu catalytic dyad located within a deep, narrow tunnel formed at the dimer interface. Site-directed mutagenesis experiments showed that the obvious differences in the active site residues that distinguish the FabA and FabZ subfamilies of dehydratases do not account for the unique ability of FabA to catalyze isomerization. Because the catalytic machinery of the two enzymes is practically indistinguishable, the structural differences observed in the shape of the substrate binding channels of FabA and FabZ lead us to hypothesize that the different shapes of the tunnels control the conformation and positioning of the bound substrate, allowing FabA, but not FabZ, to catalyze the isomerization reaction.

scholarly journals The Francisella tularensis FabI Enoyl-Acyl Carrier Protein Reductase Gene Is Essential to Bacterial Viability and Is Expressed during Infection

2012 ◽  
Vol 195 (2) ◽  
pp. 351-358 ◽  
Author(s):  
Luke C. Kingry ◽  
Jason E. Cummings ◽  
Kerry W. Brookman ◽  
Gopal R. Bommineni ◽  
Peter J. Tonge ◽  
...  
Keyword(s):  
Fatty Acid ◽  
Francisella Tularensis ◽  
Fatty Acid Biosynthesis ◽  
De Novo ◽  
Acyl Carrier Protein ◽  
Transcriptional Profiling ◽  
Acid Synthesis ◽  
Content Type ◽  
Enoyl Acp Reductase ◽  
Long Chain

ABSTRACTFrancisella tularensisis classified as a category A priority pathogen and causes fatal disseminated disease in humans upon inhalation of less than 50 bacteria. Although drugs are available for treatment, they are not ideal because of toxicity and route of delivery, and in some cases patients relapse upon withdrawal. We have an ongoing program to develop novel FAS-II FabI enoyl-ACP reductase enzyme inhibitors forFrancisellaand other select agents. To establishF. tularensisFabI (FtFabI) as a clinically relevant drug target, we demonstrated that fatty acid biosynthesis and FabI activity are essential for growth even in the presence of exogenous long-chain lipids and that FtfabIis not transcriptionally altered in the presence of exogenous long-chain lipids. Inhibition of FtFabI or fatty acid synthesis results in loss of viability that is not rescued by exogenous long-chain lipid supplementation. Importantly, whole-genome transcriptional profiling ofF. tularensiswith DNA microarrays from infected tissues revealed that FtfabIandde novofatty acid biosynthetic genes are transcriptionally active during infection. This is the first demonstration that the FabI enoyl-ACP-reductase enzyme encoded byF. tularensisis essential and not bypassed by exogenous fatty acids and thatde novofatty acid biosynthetic components encoded inF. tularensisare transcriptionally active during infection in the mouse model of tularemia.

scholarly journals Activity Mapping the Acyl Carrier Protein - Elongating Ketosynthase Interaction in Fatty Acid Biosynthesis

2020 ◽  
Author(s):  
Jeffrey T. Mindrebo ◽  
Laetitia E. Misson ◽  
Caitlin Johnson ◽  
Joseph P. Noel ◽  
Michael D. Burkart
Keyword(s):  
Fatty Acid ◽  
Active Sites ◽  
Fatty Acid Biosynthesis ◽  
Acyl Carrier Protein ◽  
Site Directed Mutagenesis ◽  
Chain Extension ◽  
Carrier Protein ◽  
Type Ii ◽  
Multiple Partner ◽  
Carbon Carbon Bond

ABSTRACTElongating ketosynthases (KSs) catalyze carbon-carbon bond forming reactions during the committed step for each round of chain extension in both fatty acid synthases (FASs) and polyketide synthases (PKSs). A small α-helical acyl carrier protein (ACP) shuttles fatty acyl intermediates between enzyme active sites. To accomplish this task, ACP relies on a series of dynamic interactions with multiple partner enzymes of FAS and associated FAS-dependent pathways. Recent structures of the Escherichia coli FAS ACP, AcpP, in covalent complexes with its two cognate elongating KSs, FabF and FabB, provide high-resolution detail of these interfaces, but a systematic analysis of specific interfacial interactions responsible for stabilizing these complexes has not yet been undertaken. Here, we use site-directed mutagenesis with both in vitro and in vivo activity analyses to quantitatively evaluate these contacting surfaces between AcpP and FabF. We delineate the FabF interface into three interacting regions and demonstrate the effects of point mutants, double mutants, and region delete variants. Results from these analyses reveal a robust and modular FabF interface capable of tolerating seemingly critical interface mutations with only the deletion of entire regions significantly compromising activity. Structure and sequence analysis of FabF orthologs from related type II FAS pathways indicate significant conservation of type II FAS KS interface residues and, overall, support its delineation into interaction regions. These findings strengthen our mechanistic understanding of molecular recognition events between ACPs and FAS enzymes and provide a blueprint for engineering ACP-dependent biosynthetic pathways.

scholarly journals Biochemical and Structural Insights Concerning Triclosan Resistance in a Novel YX7K Type Enoyl-Acyl Carrier Protein Reductase from Soil Metagenome

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Raees Khan ◽  
Amir Zeb ◽  
Kihyuck Choi ◽  
Gihwan Lee ◽  
Keun Woo Lee ◽  
...  
Keyword(s):  
Pathogenic Bacteria ◽  
Fatty Acid Biosynthesis ◽  
Catalytic Domain ◽  
Acyl Carrier Protein ◽  
Site Directed Mutagenesis ◽  
Structural Basis ◽  
Carrier Protein ◽  
The Novel ◽  
Triclosan Resistance ◽  
Structural Insights

Abstract Enoyl-acyl carrier protein reductase (ENR) catalyzes the last reduction step in the bacterial type II fatty acid biosynthesis cycle. ENRs include FabI, FabL, FabL2, FabK, and FabV. Previously, we reported a unique triclosan (TCL) resistant ENR homolog that was predominant in obligate intracellular pathogenic bacteria and Apicomplexa. Herein, we report the biochemical and structural basis of TCL resistance in this novel ENR. The purified protein revealed NADH-dependent ENR activity and shared similarity to prototypic FabI. Thus, this metagenome-derived ENR was designated FabI2. Unlike other prototypic bacterial ENRs with the YX6K type catalytic domain, FabI2 possessed a unique YX7K type catalytic domain. Computational modeling followed by site-directed mutagenesis revealed that mild resistance (20 µg/ml of minimum inhibitory concentration) of FabI2 to TCL was confined to the relatively less bulky side chain of A128. Substitution of A128 in FabI2 with bulky valine (V128) elevated TCL resistance. Phylogenetic analysis further suggested that the novel FabI2 and prototypical FabI evolved from a common short-chain dehydrogenase reductase family. To our best knowledge, FabI2 is the only known ENR shared by intracellular pathogenic prokaryotes, intracellular pathogenic lower eukaryotes, and a few higher eukaryotes. This suggests that the ENRs of prokaryotes and eukaryotes diverged from a common ancestral ENR of FabI2.

scholarly journals Biochemical and Structural Basis of Triclosan Resistance in a Novel Enoyl-Acyl Carrier Protein Reductase

2018 ◽  
Vol 62 (8) ◽  
Author(s):  
Raees Khan ◽  
Amir Zeb ◽  
Nazish Roy ◽  
Roniya Thapa Magar ◽  
Hyo Jeong Kim ◽  
...  
Keyword(s):  
Pathogenic Bacteria ◽  
Fatty Acid Biosynthesis ◽  
Acyl Carrier Protein ◽  
Site Directed Mutagenesis ◽  
Structural Basis ◽  
Carrier Protein ◽  
Content Type ◽  
Triclosan Resistance ◽  
Bacterial Type

ABSTRACTEnoyl-acyl carrier protein reductases (ENR), such as FabI, FabL, FabK, and FabV, catalyze the last reduction step in bacterial type II fatty acid biosynthesis. Previously, we reported metagenome-derived ENR homologs resistant to triclosan (TCL) and highly similar to 7-α hydroxysteroid dehydrogenase (7-AHSDH). These homologs are commonly found inEpsilonproteobacteria, a class that contains several human-pathogenic bacteria, including the generaHelicobacterandCampylobacter. Here we report the biochemical and predicted structural basis of TCL resistance in a novel 7-AHSDH-like ENR. The purified protein exhibited NADPH-dependent ENR activity but no 7-AHSDH activity, despite its high homology with 7-AHSDH (69% to 96%). Because this ENR was similar to FabL (41%), we propose that this metagenome-derived ENR be referred to as FabL2. Homology modeling, molecular docking, and molecular dynamic simulation analyses revealed the presence of an extrapolated six-amino-acid loop specific to FabL2 ENR, which prevented the entry of TCL into the active site of FabL2 and was likely responsible for TCL resistance. Elimination of this extrapolated loop via site-directed mutagenesis resulted in the complete loss of TCL resistance but not enzyme activity. Phylogenetic analysis suggested that FabL, FabL2, and 7-AHSDH diverged from a common short-chain dehydrogenase reductase family. This study is the first to report the role of the extrapolated loop of FabL2-type ENRs in conferring TCL resistance. Thus, the FabL2 ENR represents a new drug target specific for pathogenicEpsilonproteobacteria.

scholarly journals Alteration of the Fatty Acid Profile of Streptomyces coelicolor by Replacement of the Initiation Enzyme 3-Ketoacyl Acyl Carrier Protein Synthase III (FabH)

2005 ◽  
Vol 187 (11) ◽  
pp. 3795-3799 ◽  
Author(s):  
Yongli Li ◽  
Galina Florova ◽  
Kevin A. Reynolds
Keyword(s):  
Fatty Acids ◽  
Fatty Acid ◽  
Fatty Acid Biosynthesis ◽  
Acyl Carrier Protein ◽  
Streptomyces Coelicolor ◽  
Carrier Protein ◽  
Acid Biosynthesis ◽  
E Coli ◽  
Cell Extracts ◽  
Branched Chain

ABSTRACT The first elongation step of fatty acid biosynthesis by a type II dissociated fatty acid synthases is catalyzed by 3-ketoacyl-acyl carrier protein (ACP) synthase III (KASIII, FabH). This enzyme, encoded by the fabH gene, catalyzes a decarboxylative condensation between an acyl coenzyme A (CoA) primer and malonyl-ACP. In organisms such as Escherichia coli, which generate only straight-chain fatty acids (SCFAs), FabH has a substrate preference for acetyl-CoA. In streptomycetes and other organisms which produce a mixture of both SCFAs and branched-chain fatty acids (BCFAs), FabH has been shown to utilize straight- and branched-chain acyl-CoA substrates. We report herein the generation of a Streptomyces coelicolor mutant (YL/ecFabH) in which the chromosomal copy of the fabH gene has been replaced and the essential process of fatty acid biosynthesis is initiated by plasmid-based expression of the E. coli FabH (bearing only 35% amino acid identity to the Streptomyces enzyme). The YL/ecFabH mutant produces predominantly SCFAs (86%). In contrast, BCFAs predominate (∼70%) in both the S. coelicolor parental strain and S. coelicolor YL/sgFabH (a ΔfabH mutant carrying a plasmid expressing the Streptomyces glaucescens FabH). These results provide the first unequivocal evidence that the substrate specificity of FabH observed in vitro is a determinant of the fatty acid made in an organism. The YL/ecFabH strain grows significantly slower on both solid and liquid media. The levels of FabH activity in cell extracts of YL/ecFabH were also significantly lower than those in cell extracts of YL/sgFabH, suggesting that a decreased rate of fatty acid synthesis may account for the observed decreased growth rate. The production of low levels of BCFAs in YL/ecFabH suggests either that the E. coli FabH is more tolerant of different acyl-CoAs substrates than previously thought or that there is an additional pathway for initiation of BCFA biosynthesis in Streptomyces coelicolor.

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