title: Biochemical and genetic characterization of the Enterococcus faecalis oxaloacetate decarboxylase complex.
abstract: Enterococcus faecalis encodes a biotin-dependent oxaloacetate decarboxylase (OAD), which is constituted by four subunits: E. faecalis carboxyltransferase subunit OadA (termed Ef-A), membrane pump Ef-B, biotin acceptor protein Ef-D, and the novel subunit Ef-H. Our results show that in E. faecalis, subunits Ef-A, Ef-D, and Ef-H form a cytoplasmic soluble complex (termed Ef-AHD) which is also associated with the membrane. In order to characterize the role of the novel Ef-H subunit, coexpression of oad genes was performed in Escherichia coli, showing that this subunit is vital for Ef-A and Ef-D interaction. Diminished growth of the oadA and oadD single deletion mutants in citrate-supplemented medium indicated that the activity of the complex is essential for citrate utilization. Remarkably, the oadB-deficient strain was still capable of growing to wild-type levels but with a delay during the citrate-consuming phase, suggesting that the soluble Ef-AHD complex is functional in E. faecalis. These results suggest that the Ef-AHD complex is active in its soluble form, and that it is capable of interacting in a dynamic way with the membrane-bound Ef-B subunit to achieve its maximal alkalinization capacity during citrate fermentation.
authors: Instituto de Biología Molecular y Celular de Rosario (IBR-CONICET) and Departamento de Microbiología, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Rosario, Argentina.
authors: Guillermo D
authors: GD
authors: Repizo
authors: Víctor S
authors: VS
authors: Blancato
authors: Pablo
authors: P
authors: Mortera
authors: Juke S
authors: JS
authors: Lolkema
authors: Christian
authors: C
authors: Magni
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D002262:Carboxy-Lyases / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism; D019343:Citric Acid / Q000378:metabolism; D003593:Cytoplasm / Q000201:enzymology; D013293:Enterococcus faecalis / Q000201:enzymology* / Q000235:genetics / Q000502:physiology; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D005285:Fermentation; D006863:Hydrogen-Ion Concentration; D009097:Multienzyme Complexes / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism; D062907:Oxaloacetic Acid / Q000378:metabolism; D021122:Protein Subunits; D011994:Recombinant Proteins; D017384:Sequence Deletion; D019076:Transgenes
chemical_list: D001426:Bacterial Proteins; D009097:Multienzyme Complexes; D021122:Protein Subunits; D011994:Recombinant Proteins; D019343:Citric Acid; D062907:Oxaloacetic Acid; D002262:Carboxy-Lyases; C021916:oxaloacetate decarboxylase