Molecular and genetic characterization of a biotin biosynthetic gene in Arabidopsis encoding both 7,8-diaminopelargonic acid aminotransferase and dethiobiotin synthetase

Abstract

Biotin is an essential enzyme cofactor required for different metabolic processes. Plants are a major source of biotin, however, the genes and the protein products of biotin biosynthetic pathway are not fully characterized. We have molecularly characterized the genetically defined Arabidopsis biol locus as encoding 7,8diaminopelargonic acid (DAPA) aminotransferase. Molecular and genetic analysis revealed that the full length BI01 cDNA is capable of producing a fusion protein that catalyzes not only DAPA aminotransferase, but also dethiobiotin synthetase (BIOS) which is another enzymatic step in the biotin biosynthetic pathway. We refer to this fusion-gene as BI03/BI01. This bifunctional enzyme was demonstrated by functional complementation of £. coli bioA' and bioD' mutants deficient in DAPA aminotransferase and dethiobiotin synthetase reactions, respectively. This gene organization is unique in biology and establishes that the BI03/BI01 gene has dual functions.