Identification of a vegetative promoter in Myxococcus xanthus: A protein that has homology to histones

Abstract

A physical map of 330 × 10 3 base-pairs near the replication origin of Myxococcus xanthus chromosome has been established already. Using DNA fragments from this region, Northern blot hybridization analysis was carried out in order to identify the genes expressed during vegetative growth. One of the genes, tentatively designated as vegA, was cloned and its entire DNA sequence was determined. The amino acid sequence of the gene product deduced from the DNA sequence reveals that the VegA protein is a very basic protein with a molecular weight of 18,700. The gene was expressed in Escherichia coli using an expression vector, and its gene product was identified using SDS/polyacrylamide gel electrophoresis. From the results of S 1 nuclease mapping, the vegA promoter was found to contain the sequence TAGACA at the −35 region and the sequence AAGGGT at the −10 region. These two regions are separated by 18 nucleotides. Genetic analysis suggests that the vegA gene may be essential for the growth of M. xanthus. From a computer-aided search for homologies to know protein structures, it was found that the VegA protein has homologies to histone H4 of Tetrahymena thermophila and histone H2B of sea urchin.