CLONING, SEQUENCING, AND EXPRESSION OF THE RPOD GENE ENCODING THE PRIMARY SIGMA-FACTOR OF XANTHOMONAS-CAMPESTRIS

A DNA fragment encoding the primary sigma factor from Xanthomonas camp estris pv. campestris was cloned and sequenced. The gene (rpoD) encode s a polypeptide of 622 amino acids with a calculated MW of 70,700. The deduced amino acid sequence exhibits extensive sequence homology to t he conserved regions of the primary sigma factors from bacteria. The g ene product expressed in Escherichia coli, detected by Western blot an alysis, had a MW similar to that estimated for the purified protein in SDS-PAGE. The NH2-terminal amino acid sequence determined chemically matched with that deduced from the nucleotide sequence of the rpoD gen e. The calculated pI value (9.31) for the X. campestris primary sigma factor is much higher than the values observed for the analogous prote ins from other bacteria. (C) 1997 Academic Press.