PLANT PHYSIOLOGY , Vol 110, Issue 3 1021-1028, Copyright © 1996 by American Society of Plant Biologists
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BIOCHEMISTRY AND ENZYMOLOGY |
Characterization of the cDNA and Gene Coding for the Biotin Synthase of Arabidopsis thaliana
L. M. Weaver, F. Yu, E. S. Wurtele and B. J. Nikolau
Department of Biochemistry and Biophysics (L.M.W., B.J.N.) and Department of Botany (F.Y., E.S.W.), Iowa State University, Ames, Iowa 50011
Biotin, an essential cofactor, is synthesized de novo only by plants and
some microbes. An Arabidopsis thaliana expressed sequence tag that shows
sequence similarity to the carboxyl end of biotin synthase from Escherichia
coli was used to isolate a near-full-length cDNA. This cDNA was shown to
code for the Arabidopsis biotin synthase by its ability to complement a
bioB mutant of E.coli. Site-specific mutagenesis indicates that residue
threonine-173, which is highly conserved in biotin synthases, is important
for catalytic competence of the enzyme. The primary sequence of the
Arabidopsis biotin synthase is most similar to biotin synthases from E.
coli, Serratia marcescens, and Saccharomyces cerevisiae (about 50% sequence
identity) and more distantly related to the Bacillus sphaericus enzyme (33%
sequence identity). The primary sequence of the amino terminus of the
Arabidopsis biotin synthase may represent an organelle-targeting transit
peptide. The single Arabidopsis gene coding for biotin synthase, BIO2, was
isolated and sequenced. The biotin synthase coding sequence is interrupted
by five introns. The gene sequence upstream of the translation start site
has several unusual features, including imperfect palindromes and
polypyrimidine sequences, which may function in the transcriptional
regulation of the BIO2 gene.
