Publications

• Crystal structure of Spot 14, a modulator of fatty acid synthesis.

  Colbert C.L., Kim C.W., Moon Y.A., Henry L., Palnitkar M., McKean W.B., Fitzgerald K., Deisenhofer J., Horton J.D., Kwon H.J.

  Spot 14 (S14) is a protein that is abundantly expressed in lipogenic tissues and is regulated in a manner similar to other enzymes involved in fatty acid synthesis. Deletion of S14 in mice decreased lipid synthesis in lactating mammary tissue, but the mechanism of S14's action is unknown. Here we ... >> More

  Spot 14 (S14) is a protein that is abundantly expressed in lipogenic tissues and is regulated in a manner similar to other enzymes involved in fatty acid synthesis. Deletion of S14 in mice decreased lipid synthesis in lactating mammary tissue, but the mechanism of S14's action is unknown. Here we present the crystal structure of S14 to 2.65 Å and biochemical data showing that S14 can form heterodimers with MIG12. MIG12 modulates fatty acid synthesis by inducing the polymerization and activity of acetyl-CoA carboxylase, the first committed enzymatic reaction in the fatty acid synthesis pathway. Coexpression of S14 and MIG12 leads to heterodimers and reduced acetyl-CoA carboxylase polymerization and activity. The structure of S14 suggests a mechanism whereby heterodimer formation with MIG12 attenuates the ability of MIG12 to activate ACC. << Less

  Proc. Natl. Acad. Sci. U.S.A. 107:18820-18825(2010) [PubMed] [EuropePMC]

• Propionyl coenzyme A (propionyl-CoA) carboxylase in Haloferax mediterranei: Indispensability for propionyl-CoA assimilation and impacts on global metabolism.

  Hou J., Xiang H., Han J.

  Propionyl coenzyme A (propionyl-CoA) is an important intermediate during the biosynthesis and catabolism of intracellular carbon storage of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) in haloarchaea. However, the haloarchaeal propionyl-CoA carboxylase (PCC) and its physiological significan ... >> More

  Propionyl coenzyme A (propionyl-CoA) is an important intermediate during the biosynthesis and catabolism of intracellular carbon storage of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) in haloarchaea. However, the haloarchaeal propionyl-CoA carboxylase (PCC) and its physiological significance remain unclear. In this study, we identified a PCC that catalyzed propionyl-CoA carboxylation with an acetyl-CoA carboxylation side activity in Haloferax mediterranei. Gene knockout/complementation demonstrated that the PCC enzyme consisted of a fusion protein of a biotin carboxylase and a biotin-carboxyl carrier protein (PccA [HFX_2490]), a carboxyltransferase component (PccB [HFX_2478]), and an essential small subunit (PccX [HFX_2479]). Knockout of pccBX led to an inability to utilize propionate and a higher intracellular propionyl-CoA level, indicating that the PCC enzyme is indispensable for propionyl-CoA utilization. Interestingly, H. mediterranei DBX (pccBX-deleted strain) displayed multiple phenotypic changes, including retarded cell growth, decreased glucose consumption, impaired PHBV biosynthesis, and wrinkled cells. A propionyl-CoA concentration equivalent to the concentration that accumulated in DBX cells was demonstrated to inhibit succinyl-CoA synthetase of the tricarboxylic acid cycle in vitro. Genome-wide microarray analysis showed that many genes for glycolysis, pyruvate oxidation, PHBV accumulation, electron transport, and stress responses were affected in DBX. This study not only identified the haloarchaeal PCC for the metabolism of propionyl-CoA, an important intermediate in haloarchaea, but also demonstrated that impaired propionyl-CoA metabolism affected global metabolism in H. mediterranei. << Less

  Appl. Environ. Microbiol. 81:794-804(2015) [PubMed] [EuropePMC]

• Biochemical and molecular biological characterization of CAC2, the Arabidopsis thaliana gene coding for the biotin carboxylase subunit of the plastidic acetyl-coenzyme A carboxylase.

  Sun J., Ke J., Johnson J.L., Nikolau B.J., Wurtele E.S.

  The biotin carboxylase subunit of the heteromeric chloroplastic acetyl-coenzyme A carboxylase (ACCase) of Arabidopsis thaliana is coded by a single gene (CAC2), which is interrupted by 15 introns. The cDNA encodes a deduced protein of 537 amino acids with an apparent N-terminal chloroplast-targeti ... >> More

  The biotin carboxylase subunit of the heteromeric chloroplastic acetyl-coenzyme A carboxylase (ACCase) of Arabidopsis thaliana is coded by a single gene (CAC2), which is interrupted by 15 introns. The cDNA encodes a deduced protein of 537 amino acids with an apparent N-terminal chloroplast-targeting transit peptide. Antibodies generated to a glutathione S-transferase-CAC2 fusion protein react solely with a 51-kD polypeptide of Arabidopsis; these antibodies also inhibit ACCase activity in extracts of Arabidopsis. The entire CAC2 cDNA sequence was expressed in Escherichia coli and the resulting recombinant biotin carboxylase was enzymatically active in carboxylating free biotin. The catalytic properties of the recombinant biotin carboxylase indicate that the activity of the heteromeric ACCase may be regulated by light-/dark-induced changes in stromal pH. The CAC2 gene is maximally expressed in organs and tissues that are actively synthesizing fatty acids for membrane lipids or oil deposition. The observed expression pattern of CAC2 mirrors that previously reported for the CAC1 gene (J.-K. Choi, F. Yu, E.S. Wurtele, B.J. Nikolau [1995] Plant Physiol 109: 619-625; J. Ke, J.-K. Choi, M. Smith, H.T. Horner, B.J. Nikolau, E.S. Wurtele [1997] Plant Physiol 113: 357-365), which codes for the biotin carboxyl carrier subunit of the heteromeric ACCase. This coordination is probably partially established by coordinate transcription of the two genes. This hypothesis is consistent with the finding that the CAC2 and CAC1 gene promoters share a common set of sequence motifs that may be important in guiding the transcription of these genes. << Less

  Plant Physiol. 115:1371-1383(1997) [PubMed] [EuropePMC]

• Enzymatic carboxylation of biotin: molecular and catalytic properties of a component enzyme of acetyl CoA carboxylase.

  Dimroth P., Guchhait R.B., Stoll E., Lane M.D.

  The biotin carboxylase component of acetyl CoA carboxylase has been purified approximately 2000 times from Escherichia coli. This protein, which catalyzes the carboxylation of free d-biotin, is free of the biotin-containing carboxyl carrier protein, is homogeneous by polyacrylamide gel electrophor ... >> More

  The biotin carboxylase component of acetyl CoA carboxylase has been purified approximately 2000 times from Escherichia coli. This protein, which catalyzes the carboxylation of free d-biotin, is free of the biotin-containing carboxyl carrier protein, is homogeneous by polyacrylamide gel electrophoresis and analytical ultracentrifugation, and has been crystallized. Biotin carboxylase, with a molecular weight of approximately 100,000, is composed of two 50,000-dalton subunits. The catalytic capacity of biotin carboxylase is markedly enhanced by ethanol (11 times at 15% v/v), and certain other organic solvents; this may mimic an effector-mediated response. The kinetic effect is exclusively on the maximal velocity of the reaction. Activation by ethanol is reversible and not accompanied by aggregation or disaggregation of the enzyme. << Less

  Proc Natl Acad Sci U S A 67:1353-1360(1970) [PubMed] [EuropePMC]