title: Functional complementation between the PDX1 vitamin B6 biosynthetic gene of Cercospora nicotianae and pdxJ of Escherichia coli.
abstract: The pathway for de novo vitamin B(6) biosynthesis has been characterized in Escherichia coli, however plants, fungi, archaebacteria, and most bacteria utilize an alternative pathway. Two unique genes of the alternative pathway, PDX1 and PDX2, have been described. PDX2 encodes a glutaminase, however the enzymatic function of the product encoded by PDX1 is not known. We conducted reciprocal transformation experiments to determine if there was functional homology between the E. coli pdxA and pdxJ genes and PDX1 of Cercospora nicotianae. Although expression of pdxJ and pdxA in C. nicotianae pdx1 mutants, either separately or together, failed to complement the pyridoxine mutation in this fungus, expression of PDX1 restored pyridoxine prototrophy to the E. coli pdxJ mutant. Expression of PDX1 in the E. coli pdxA mutant restored very limited ability to grow on medium lacking pyridoxine. We conclude that the PDX1 gene of the alternative B(6) pathway encodes a protein responsible for synthesis of the pyridoxine ring.
authors.affiliation: Department of Botany, North Carolina State University, Raleigh, NC 27695-7612, USA.
authors.forename: Denise K
authors.initials: DK
authors.lastname: Wetzel
authors.forename: Marilyn
authors.initials: M
authors.lastname: Ehrenshaft
authors.forename: Sheri A
authors.initials: SA
authors.lastname: Denslow
authors.forename: Margaret E
authors.initials: ME
authors.lastname: Daub
mesh_terms: D001203:Ascomycota / Q000235:genetics*; D003001:Cloning, Molecular; D004798:Enzymes / Q000502:physiology; D029968:Escherichia coli Proteins / Q000235:genetics / Q000502:physiology*; D005656:Fungal Proteins / Q000235:genetics / Q000502:physiology*; D005800:Genes, Fungal; D005816:Genetic Complementation Test; D008025:Ligases / Q000235:genetics / Q000502:physiology*; D010088:Oxidoreductases; D011736:Pyridoxine / Q000096:biosynthesis; D014170:Transformation, Genetic; D025101:Vitamin B 6 / Q000096:biosynthesis*
chemical_list: D004798:Enzymes; D029968:Escherichia coli Proteins; D005656:Fungal Proteins; C113268:PDX1 protein, Cercospora nicotianae; C098854:PdxJ protein, E coli; C060787:pdxA protein, E coli; D025101:Vitamin B 6; D010088:Oxidoreductases; D008025:Ligases; D011736:Pyridoxine