Identification and characterization of BpH2, a novel histone H1 homolog in Bordetella pertussis

A basic protein, BpH2, with an apparent molecular mass of 18 kDa was purified from Bordetella pertussis, and the corresponding gene, bph2, was cloned. Sequence analysis revealed some homology to the H1 class of eukaryotic histones and to AlgP protein of Pseudomonas aeruginosa. BpH2 binds both single- and double-stranded DNA in a nonspecific manner. Deletion of the corresponding gene in B. pertussis generated a BpH2 null mutant with an altered growth rate in which the expression of two virulence factors, adenylate cyclase-hemolysin (CyaA) and filamentous hemagglutinin (FhaB), was reduced. It is suggested that BpH2 may exhibit specific regulatory functions through its interaction with chromosomal DNA.