Structures of β-Ketoacyl-Acyl Carrier Protein Synthase I Complexed with Fatty Acids Elucidate its Catalytic Machinery

Olsen, Johan G.; Kadziola, Anders; Wettstein-Knowles, Penny von; Siggaard-Andersen, Marie-Louise; Larsen, Sine

doi:10.1016/s0969-2126(01)00583-4

Cited by 107 publications

(145 citation statements)

References 46 publications

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“…The inter-subunit interactions of these domains closely resemble the oligomerization modes of their monofunctional homologues (Olsen et al 2001 ;Shimomura et al 2003). Their respective contact sites directly involve the core catalytic parts, not just additional insertions, and are crucial for the integrity and catalytic activity of both domains.…”

Section: Overall Architecture and Linkersmentioning

confidence: 89%

Structure and function of eukaryotic fatty acid synthases

Maier

Leibundgut

Boehringer

et al. 2010

Quart. Rev. Biophys.

123

127

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Abstract. In all organisms, fatty acid synthesis is achieved in variations of a common cyclic reaction pathway by stepwise, iterative elongation of precursors with two-carbon extender units. In bacteria, all individual reaction steps are carried out by monofunctional dissociated enzymes, whereas in eukaryotes the fatty acid synthases (FASs) have evolved into large multifunctional enzymes that integrate the whole process of fatty acid synthesis. During the last few years, important advances in understanding the structural and functional organization of eukaryotic FASs have been made through a combination of biochemical, electron microscopic and X-ray crystallographic approaches. They have revealed the strikingly different architectures of the two distinct types of eukaryotic FASs, the fungal and the animal enzyme system. Fungal FAS is a 2Á6 MDa a 6 b 6 heterododecamer with a barrel shape enclosing two large chambers, each containing three sets of active sites separated by a central wheel-like structure. It represents a highly specialized micro-compartment strictly optimized for the production of saturated fatty acids. In contrast, the animal FAS is a 540 kDa X-shaped homodimer with two lateral reaction clefts characterized by a modular domain architecture and large extent of conformational flexibility that appears to contribute to catalytic efficiency.

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Section: Overall Architecture and Linkersmentioning

confidence: 89%

Structure and function of eukaryotic fatty acid synthases

Maier

Leibundgut

Boehringer

et al. 2010

Quart. Rev. Biophys.

123

127

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“…PctT is thus proposed to catalyze the priming reaction with acetyl CoA onto a discrete ACP PctK, which would be specifically recognized by an iterative type I PKS PctS for the formation of 6-MSA. FabB enzymes serve a relatively large active site cavity and catalyze the condensation of a wide range of acyl-ACPs [57]. Therefore, its homologous protein PctM might recognize the attached 6-MSA-ACP thioester in the active site of PctS, and catalyze a transfer reaction onto a hydroxy group in the core cyclopentane ring to form an ester bond (Fig.…”

Section: Functional Analysis Of the Pctl Gene Encoding A Glycosyltranmentioning

confidence: 99%

Cloning of the Pactamycin Biosynthetic Gene Cluster and Characterization of a Crucial Glycosyltransferase Prior to a Unique Cyclopentane Ring Formation

et al. 2007

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The biosynthetic gene (pct) cluster for an antitumor antibiotic pactamycin was identified by use of a gene for putative radical S-adenosylmethionine methyltransferase as a probe. The pct gene cluster is localized to a 34 kb contiguous DNA from Streptomyces pactum NBRC 13433 and contains 24 open reading frames. Based on the bioinformatic analysis, a plausible biosynthetic pathway for pactamycin comprising of a unique cyclopentane ring, 3-aminoacetophenone, and 6-methylsalicylate was proposed. The pctL gene encoding a glycosyltransferase was speculated to be involved in an N-glycoside formation between 3-aminoacetophenone and UDP-N-acetyl-a -D-glucosamine prior to a unique cyclopentane ring formation. The pctL gene was then heterologously expressed in Escherichia coli and the enzymatic activity of the recombinant PctL protein was investigated. Consequently, the PctL protein was found to catalyze the expected reaction forming b-N-glycoside. The enzymatic activity of the PctL protein clearly confirmed that the present identified gene cluster is for the biosynthesis of pactamycin. Also, a glycosylation prior to cyclopentane ring formation was proposed to be a general strategy in the biosynthesis of the structurally related cyclopentane containing compounds.

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“…It is interesting to note that some members belonging to the thiolase fold family possess the capability to use long aliphatic chains as substrates (15,36,37). The analysis of the three-dimensional crystal structure of KAS III enzyme (1HZP) from M. tuberculosis (referred to as mtFabH) has revealed the mechanism by which it can catalyze the decarboxylative condensation of bulky myristoyl-CoA with malonyl-acyl carrier protein.…”

Section: Figmentioning

confidence: 99%

“…Using the program ACSITE (40), an elongated cavity was identified in mtFabH along the dimer interface, indicating that elongated substrate can be accommodated in the active site of the 1HZP fold. Since the mtFabH coordinates complexed with substrate are not available in the Protein Data Bank, lauric acid was modeled in the active site of PKS18 using the information from the crystal structure of lauric acid-KAS I complex (1EK4) (37). Although KAS I proteins have no detectable sequence homology to the CHS family of condensing proteins, crystal structure analysis has revealed a conserved thiolase fold (41).…”

Section: Figmentioning

confidence: 99%

A New Family of Type III Polyketide Synthases in Mycobacterium tuberculosis

Saxena

Yadav²,

Mohanty

et al. 2003

Journal of Biological Chemistry

105

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The Mycobacterium tuberculosis genome has revealed a remarkable array of polyketide synthases (PKSs); however, no polyketide product has been isolated thus far. Most of the PKS genes have been implicated in the biosynthesis of complex lipids. We report here the characterization of two novel type III PKSs from M. tuberculosis that are involved in the biosynthesis of long-chain ␣-pyrones. Measurement of steady-state kinetic parameters demonstrated that the catalytic efficiency of PKS18 protein was severalfold higher for long-chain acyl-coenzyme A substrates as compared with the smallchain precursors. The specificity of PKS18 and PKS11 proteins toward long-chain aliphatic acyl-coenzyme A (C 12 to C 20 ) substrates is unprecedented in the chalcone synthase (CHS) family of condensing enzymes. Based on comparative modeling studies, we propose that these proteins might have evolved by fusing the catalytic machinery of CHS and ␤-ketoacyl synthases, the two evolutionarily related members with conserved thiolase fold. The mechanistic and structural importance of several active site residues, as predicted by our structural model, was investigated by performing site-directed mutagenesis. The functional identification of diverse catalytic activity in mycobacterial type III PKSs provide a fascinating example of metabolite divergence in CHSlike proteins.Mycobacteria are classified in the phylogeny of the Actinomycetes, along with the Streptomyces bacteria. Interestingly, these two actinomycete genera have received immense attention due to their contrasting effects on human society. Whereas Streptomyces have provided a rich source of antibiotics and other therapeutic products for human diseases, Mycobacterium tuberculosis and Mycobacterium leprae have been two of humankind's greatest scourges. Although the original phylogenic classifications of Mycobacterium and Streptomyces were based primarily on morphology, the genome sequences of these organisms have further established their common lineage (1, 2). These genome sequences have revealed several families of genes that are common between them, which include an unusually large number of gene clusters that are homologous to polyketide synthases (PKSs). 1 Although a polyketide producthas not yet been isolated from M. tuberculosis, recent studies have implicated some of its PKS genes in the biosynthesis of complex lipids (3). In this report, we have characterized two novel polyketide synthases from M. tuberculosis, which are involved in the biosynthesis of unusual long-chain ␣-pyrones.Polyketides are a diverse class of secondary metabolites that possess a broad range of biological activities (4). Despite structural diversity of these natural products, PKSs synthesize polyketides by a common chemical strategy. Initial priming by a starter molecule is followed by repetitive decarboxylative condensation of coenzyme A (CoA) analogues of simple carboxylic acids. PKS elongates the polyketide chain either by repetitively using a single active site to perform multiple condensation reaction...

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Structures of β-Ketoacyl-Acyl Carrier Protein Synthase I Complexed with Fatty Acids Elucidate its Catalytic Machinery

Cited by 107 publications

References 46 publications

Structure and function of eukaryotic fatty acid synthases

Structure and function of eukaryotic fatty acid synthases

Cloning of the Pactamycin Biosynthetic Gene Cluster and Characterization of a Crucial Glycosyltransferase Prior to a Unique Cyclopentane Ring Formation

A New Family of Type III Polyketide Synthases in Mycobacterium tuberculosis

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