Component X of mammalian pyruvate dehydrogenase complex: Structural and functional relationship to the lipoate acetyltransferase (E2) component

Neagle, J.; Marcucci, Olga De; Dunbar, Bryan; Lindsay, J. Gordon

doi:10.1016/0014-5793(89)80919-6

Cited by 45 publications

(46 citation statements)

References 22 publications

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“…The E3-binding protein (E3BP) is homologous to E2 subunits and includes a single lipoyl domain followed by a peripheral-subunit-binding domain (PSBD) and the catalytic domain (77,155). The lipoyl domain is lipoylated and can be reduced and acetylated by the E3 and E1 subunits of PDH (85,100,181).…”

Section: Lipoylated Complexesmentioning

confidence: 99%

Lipoic Acid Metabolism in Microbial Pathogens

Spalding

Prigge

2010

Microbiol Mol Biol Rev

165

204

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SUMMARY Lipoic acid [(R)-5-(1,2-dithiolan-3-yl)pentanoic acid] is an enzyme cofactor required for intermediate metabolism in free-living cells. Lipoic acid was discovered nearly 60 years ago and was shown to be covalently attached to proteins in several multicomponent dehydrogenases. Cells can acquire lipoate (the deprotonated charge form of lipoic acid that dominates at physiological pH) through either scavenging or de novo synthesis. Microbial pathogens implement these basic lipoylation strategies with a surprising variety of adaptations which can affect pathogenesis and virulence. Similarly, lipoylated proteins are responsible for effects beyond their classical roles in catalysis. These include roles in oxidative defense, bacterial sporulation, and gene expression. This review surveys the role of lipoate metabolism in bacterial, fungal, and protozoan pathogens and how these organisms have employed this metabolism to adapt to niche environments.

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Section: Lipoylated Complexesmentioning

confidence: 99%

Lipoic Acid Metabolism in Microbial Pathogens

Spalding

Prigge

2010

Microbiol Mol Biol Rev

165

204

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“…E3BP (previously known as protein X) provides primarily the binding site for E3 (3,4). In the absence of E3BP, PDC catalysis is supported at a rate of 4% only (5,6). Both E2 and E3BP share considerable sequence identity (37%) as revealed in pairwise sequence alignment (7).…”

mentioning

confidence: 99%

“…Both E2 and E3BP share considerable sequence identity (37%) as revealed in pairwise sequence alignment (7). The principal differences are that mammalian E3BP has a single lipoyl domain compared with two lipoyl domains in E2 and lacks the conserved active-site histidine residue that is essential for acetyltransferase activity (5,8). These two proteins are of particular importance for selective binding of E1 and E3 to higher eukaryotic PDC core structures.…”

mentioning

confidence: 99%

How Dihydrolipoamide Dehydrogenase-binding Protein Binds Dihydrolipoamide Dehydrogenase in the Human Pyruvate Dehydrogenase Complex

Ciszak

Makal

Hong

et al. 2006

Journal of Biological Chemistry

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The dihydrolipoamide dehydrogenase-binding protein (E3BP) and the dihydrolipoamide acetyltransferase (E2) component enzyme form the structural core of the human pyruvate dehydrogenase complex by providing the binding sites for two other component proteins, dihydrolipoamide dehydrogenase (E3) and pyruvate dehydrogenase (E1), as well as pyruvate dehydrogenase kinases and phosphatases. Despite a high similarity between the primary structures of E3BP and E2, the E3-binding domain of human E3BP is highly specific to human E3, whereas the E1-binding domain of human E2 is highly specific to human E1. In this study, we characterized binding of human E3 to the E3-binding domain of E3BP by x-ray crystallography at 2.6-Å resolution, and we used this structural information to interpret the specificity for selective binding. Two subunits of E3 form a single recognition site for the E3-binding domain of E3BP through their hydrophobic interface. The hydrophobic residues Pro 133 , Pro 154 , and Ile 157 in the E3-binding domain of E3BP insert themselves into the surface of both E3 polypeptide chains. Numerous ionic and hydrogen bonds between the residues of three interacting polypeptide chains adjacent to the central hydrophobic patch add to the stability of the subcomplex. The specificity of pairing for human E3BP with E3 is interpreted from its subcomplex structure to be most likely due to conformational rigidity of the binding fragment of the E3-binding domain of E3BP and its exquisite amino acid match with the E3 target interface. The human pyruvate dehydrogenase complex (PDC)2 with an approximate molecular mass of 8 ϫ 10 6 Da consists of multiple copies of three catalytic enzymes known as pyruvate dehydrogenase (E1), dihydrolipoamide acetyltransferase (E2), and dihydrolipoamide dehydrogenase (E3) as well as the dedicated E3-binding protein (E3BP) (1). In addition, pyruvate dehydrogenase kinase and phosphatase interacting with the complex are responsible for regulation of PDC activity by a reversible phosphorylation/dephosphorylation mechanism that involves covalent modification of E1. PDC plays a key role in regulation of the flux of two-carbon acetyl units from pyruvate through acetyl-CoA into the Krebs cycle, yielding CO 2 , NADH, and H ϩ . The E1 component catalyzes the decarboxylation of pyruvate and the reductive acetylation of the lipoyl moieties of E2. The E2 component transfers the acetyl group to CoA. The E3 component oxidizes the reduced lipoyl moieties through reduction of NAD ϩ to NADH, thus preparing the lipoyl moiety for another cycle of catalytic reaction. Along with E3BP, the human E2 component forms the structural core of PDC and provides the binding site for E1 (2). E3BP (previously known as protein X) provides primarily the binding site for E3 (3, 4). In the absence of E3BP, PDC catalysis is supported at a rate of 4% only (5, 6). Both E2 and E3BP share considerable sequence identity (37%) as revealed in pairwise sequence alignment (7). The principal differences are that mammalian E3BP has a single lipoyl ...

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“…20 Whereas the E3BP subunit is distinct from E2 subunits, it too exhibits this motif, as it has a N-terminal region of lysine-lipoyl domains, a subunit binding domain, and an inner core domain. [21][22][23][24] Very extensive studies have mapped the autoepitopes recognized by B cells through the use of recombinant proteins, truncated constructs, and a combination of peptides. These studies have shown that the immune reactivity of AMA is directed against a conformational epitope that includes a lysine-lipoyl domain.…”

Section: P Rimary Biliary Cirrhosis (Pbc) Is An Archetypicalmentioning

confidence: 99%

Sidechain Biology and the Immunogenicity of Pdc–E2, the Major Autoantigen of Primary Biliary Cirrhosis

Mao

Davis

Odin³

et al. 2004

Hepatology

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The E2 component of mitochondrial pyruvate dehydrogenase complex (PDC-E2) is the immunodominant autoantigen of primary biliary cirrhosis. Whereas lipoylation of PDC-E2 is essential for enzymatic activity and predominates under normal conditions, other biochemical systems exist that also target the lysine residue, including acylation of fatty acids or xenobiotics and ubiquitinylation. More importantly, the immunogenicity can be affected by derivatization of the lysine residue, as the recognition of lipoylated PDC-E2 by patient autoantibodies is enhanced compared with octanoylated PDC-E2. Furthermore, our laboratory has shown that various xenobiotic modifications of a peptide representing the immunodominant region of PDC-E2 are immunoreactive against patient sera. The only purported regulatory system that prevents the accumulation of potentially autoreactive PDC-E2 is glutathionylation, in which the lysine-lipoic acid moiety is further modified with glutathione during apoptosis. Interestingly, this system is found in several cell lines, including HeLa, Jurkat, and Caco-2 cells, but not in cholangiocytes and salivary gland epithelial cells, both of which are targets for destruction in primary biliary cirrhosis. Hence, the failure of this or other regulatory system(s) may overwhelm the immune system with immunogenic PDC-E2 that can initiate the breakdown of tolerance in a genetically susceptible individual. In this review the authors survey the data available on the biochemical life of PDC-E2, with particular emphasis on the lysine residue and its known interactions with machinery involved in various posttranslational modifications. (HEPATOLOGY 2004;40:1241-1248 P rimary biliary cirrhosis (PBC) is an archetypical organ-specific autoimmune disease that predominantly affects middle-aged women and includes a chronic and progressive inflammatory response, leading to destruction of intrahepatic bile duct epithelial cells (cholangiocytes). The diagnostic hallmark of PBC is the antimitochondrial antibody (AMA) that reacts specifically with E2 components of 2-oxoacid dehydrogenase enzymes, particularly the 74-kd E2 subunit of the pyruvate dehydrogenase complex (PDC-E2); 90% to 95% of patients with PBC have high titer AMAs long before onset of clinical symptoms. 1,2 We believe that a thorough understanding of the biochemical nature of enzymatic interactions of PDC-E2 is key to unraveling the enigma of PBC.Pyruvate Dehydrogenase Complex. PDC is a noncovalent enzymatic complex that catalyzes the oxidative decarboxylation of pyruvate to acetyl CoA. The complex consists of a multimer core of dihydrolipoyl transacetylase (E2) chains arranged with icosahedral symmetry on which the other protein components are arranged. 3 The role of E2 to shuttle an acetyl group to CoA to produce acetyl CoA is supported by the structure of the protein wherein the lysine side-chain derivatized by the lipoic acid is mobile and exposed to solvent. PDC is a critical enzyme in the control of intermediate metabolism because it modulates carbohydrate met...

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Component X of mammalian pyruvate dehydrogenase complex: Structural and functional relationship to the lipoate acetyltransferase (E2) component

Cited by 45 publications

References 22 publications

Lipoic Acid Metabolism in Microbial Pathogens

Lipoic Acid Metabolism in Microbial Pathogens

How Dihydrolipoamide Dehydrogenase-binding Protein Binds Dihydrolipoamide Dehydrogenase in the Human Pyruvate Dehydrogenase Complex

Sidechain Biology and the Immunogenicity of Pdc–E2, the Major Autoantigen of Primary Biliary Cirrhosis

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