Biotin synthesis in higher plants: isolation of a cDNA encoding Arabidopsis thaliana bioB-gene product equivalent by functional complementation of a biotin auxotroph mutant bioB105 of Escherichia coli K12.

Biotin synthase is involved in the conversion of dethiobiotin to biotin in bacteria, yeast and higher plants. We isolated a complete cDNA (1.3 kb) encoding A. thaliana bioB-gene product by functional complementation of the bioB105 biotin auxotroph mutant of Escherichia coli K12 using an A. thaliana cDNA library. The open reading frame encodes a predicted protein of 378 amino acids and molecular mass of 41.634 Da. The bioB-gene product from A. thaliana shows specific regions of homology with the bioB-gene products of E. coli, Serratia marcescens, Bacillus sphaericus, and Saccharomyces cerevisiae. The predicted amino acid sequence of the plant protein contains the consensus region GXCXEDCXYCXQ involved in the [2Fe-2S] cluster binding. Furthermore, it does not present a transit peptide in its N-terminal region suggesting that the A. thaliana bioB-gene product reported in this paper is located in the cytosolic compartment.