Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:6.4.1.2 (acetyl-CoA carboxylase)
 2,876 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The role of the alpha-thyroid hormone receptor (TR alpha) in regulation of transcription of the gene for chicken malic enzyme was analyzed in fibroblast cell lines normally unresponsive to triiodothyronine (T3). The gene for this transcription factor was introduced stably and overexpressed using a replication-competent retroviral vector. In chick embryo fibroblasts (CEF), overexpression of TR alpha decreased malic enzyme activity by 90% in the absence of T3. Addition of T3 almost completely restored malic enzyme activity to the level of similarly treated control CEF infected with virus lacking TR alpha. These TR alpha-induced changes in malic enzyme activity were mediated by alterations in transcription of the malic enzyme gene. Similar results were obtained when transcriptional activity of TR alpha was analyzed using a transient co-transfection system. Thus, the unliganded TR alpha is a transcriptional repressor of the malic enzyme gene; binding of T3 to the receptor abolishes this repression. In contrast, stable overexpression of TR alpha in QT6 cells had no effect on malic enzyme expression in the absence or presence of T3. Nuclear T3 binding was equally high in CEF and QT6 cells overexpressing TR alpha. These findings suggest that cell-specific factors control the ability of TR alpha to regulate the malic enzyme gene. Overexpression of TR alpha in CEF had no effect on the expression of fatty acid synthase and acetyl-CoA carboxylase, lipogenic enzymes that are stimulated by T3 in hepatocytes in culture. Thus, gene-specific factors also may control the transcriptional activity of TR alpha.
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PMID:Overexpression of the alpha-thyroid hormone receptor in avian cell lines. Effects on expression of the malic enzyme gene are selective and cell-specific. 135 Oct 57

The Escherichia coli repressor of biotin biosynthesis (BirA) is a unique transcriptional repressor which catalyzes synthesis of its own corepressor and catalyzes attachment of a cofactor to an essential metabolic enzyme. BirA both catalyzes synthesis of biotinyl-5'-AMP from the substrates ATP and biotin and transfer of the biotin moiety from the adenylate to a lysine residue of a subunit of the acetyl-CoA carboxylase. BirA-bio-5'-AMP, moreover, binds sequence specifically to the biotin operator to repress transcription of the biotin biosynthetic genes. Using a combination of kinetic measurements of binding of the two ligands, biotin and bio-5'-AMP, to BirA as well as proteolytic digestion experiments, we have found evidence for at least three discrete conformational states of BirA. Results of stopped-flow fluorescence measurements of association of both ligands with BirA indicate that the process involves initial formation of a collision complex followed by a slow conformational change. The kinetics of the conformational change are distinct for the two ligands and are the basis for the difference in the thermodynamic stabilities of the two protein-ligand complexes. Different rates of proteolytic digestion of apoBirA and complexes of BirA with the two ligands were also observed. Results of the combined approaches indicate that apoBirA, and the BirA-bio-5'-AMP and BirA-biotin complexes are conformationally distinct.
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PMID:Evidence for distinct ligand-bound conformational states of the multifunctional Escherichia coli repressor of biotin biosynthesis. 852 35

Biotin biosynthesis and retention in Escherichia coli is regulated by the multifunctional protein, BirA. The protein acts as both the transcriptional repressor of the biotin biosynthetic operon and as a ligase for covalent attachment of biotin to a unique lysine residue of the acetyl-CoA carboxylase. Biotinyl-5'-AMP is the activated intermediate for the ligase reaction and the allosteric effector for DNA binding. We have purified and characterized apoBCCP and a truncated form containing the COOH-terminal 87 residues (apoBCCP87). Molecular masses of the proteins measured using matrix-assisted laser desorption ionization time-of-flight mass spectrometry conformed to the expected values. The assembly states of apoBCCP and apoBCCP87 were determined using sedimentation equilibrium ultracentrifugation. Nearly quantitative enzymatic transfer of biotin from BirA-biotinyl-5'-AMP to the apoBCCP forms was assessed using two methods, mass spectrometric analysis of acceptor proteins after incubation with BirA-bio-5'-AMP and a steady state fluorescence assay. The BirA catalyzed rates of transfer of biotin from bio-5'-AMP to apoBCCP and apoBCCP87 were measured by stopped-flow fluorescence. Kinetic parameters estimated from these measurements indicate that the intact and truncated forms of the acceptor protein are functionally identical.
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PMID:Purification and characterization of intact and truncated forms of the Escherichia coli biotin carboxyl carrier subunit of acetyl-CoA carboxylase. 863 88

Proteins can perform completely distinct functions in response to the particular partners that they bind to. Consequently, determination of the mechanism of functional regulation in such systems requires elucidation of the mechanism switching between binding partners. The central protein of the Escherichia coli biotin regulatory system, BirA, switches between its function as a metabolic enzyme or a transcriptional repressor in response to binding either the biotin carboxyl carrier protein subunit of acetyl-CoA carboxylase or a second BirA monomer. These two protein-protein interactions are structurally mutually exclusive. The results of earlier studies suggest that the system is regulated by kinetic partitioning between the two protein-protein interactions. In this work, sedimentation velocity was employed to monitor the partitioning directly. The results indicate similar equilibrium parameters governing formation of the two protein-protein interactions. Kinetic analysis of the sedimentation velocity data indicated that holoBirA dimerization is governed by very slow forward and reverse rate constants. The slow kinetics of holoBirA dimerization combined with fluctuations in the intracellular apoBCCP pool are critical determinants in partitioning BirA between its distinct biological functions.
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PMID:Kinetic partitioning between alternative protein-protein interactions controls a transcriptional switch. 1850 76

Membrane phospholipids typically contain fatty acids (FAs) of 16 and 18 carbon atoms. This particular chain length is evolutionarily highly conserved and presumably provides maximum stability and dynamic properties to biological membranes in response to nutritional or environmental cues. Here, we show that the relative proportion of C16 versus C18 FAs is regulated by the activity of acetyl-CoA carboxylase (Acc1), the first and rate-limiting enzyme of FA de novo synthesis. Acc1 activity is attenuated by AMPK/Snf1-dependent phosphorylation, which is required to maintain an appropriate acyl-chain length distribution. Moreover, we find that the transcriptional repressor Opi1 preferentially binds to C16 over C18 phosphatidic acid (PA) species: thus, C16-chain containing PA sequesters Opi1 more effectively to the ER, enabling AMPK/Snf1 control of PA acyl-chain length to determine the degree of derepression of Opi1 target genes. These findings reveal an unexpected regulatory link between the major energy-sensing kinase, membrane lipid composition, and transcription.
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PMID:Regulation of gene expression through a transcriptional repressor that senses acyl-chain length in membrane phospholipids. 2496 Jun 95

Biotin protein ligase (BPL) inhibitors are a novel class of antibacterial that target clinically important methicillin-resistant Staphylococcus aureus (S. aureus). In S. aureus, BPL is a bifunctional protein responsible for enzymatic biotinylation of two biotin-dependent enzymes, as well as serving as a transcriptional repressor that controls biotin synthesis and import. In this report, we investigate the mechanisms of action and resistance for a potent anti-BPL, an antibacterial compound, biotinyl-acylsulfamide adenosine (BASA). We show that BASA acts by both inhibiting the enzymatic activity of BPL in vitro, as well as functioning as a transcription co-repressor. A low spontaneous resistance rate was measured for the compound (<10-9) and whole-genome sequencing of strains evolved during serial passaging in the presence of BASA identified two discrete resistance mechanisms. In the first, deletion of the biotin-dependent enzyme pyruvate carboxylase is proposed to prioritize the utilization of bioavailable biotin for the essential enzyme acetyl-CoA carboxylase. In the second, a D200E missense mutation in BPL reduced DNA binding in vitro and transcriptional repression in vivo. We propose that this second resistance mechanism promotes bioavailability of biotin by derepressing its synthesis and import, such that free biotin may outcompete the inhibitor for binding BPL. This study provides new insights into the molecular mechanisms governing antibacterial activity and resistance of BPL inhibitors in S. aureus.
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PMID:Advanced Resistance Studies Identify Two Discrete Mechanisms in Staphylococcus aureus to Overcome Antibacterial Compounds that Target Biotin Protein Ligase. 3226 15