GENES ENCODING HIGH-MOLECULAR-WEIGHT ADHESION PROTEINS OF NONTYPABLE HAEMOPHILUS-INFLUENZAE ARE PART OF GENE CLUSTERS

We previously reported the cloning and sequencing of genes designated hmw1 and hmw2 from a prototype nontypeable Haemophilus influenzae stra in. The genes encode proteins which are related to filamentous hemaggl utinin of Bordetella pertussis and promote attachment of the nontypeab le H. influenzae strain to human epithelial cells (J. W. St. Geme III, S. Falkow, and S. J. Barenkamp, Proc. Natl. Acad. Sci. USA 90:2875-28 79, 1993). Subcloning studies suggested that correct processing of the se high-molecular-weight proteins required the products of additional downstream genes. In the present study we analyzed the 3'-flanking reg ions of the hmw1A and hmw2A structural genes and found that bath genes are flanked by two additional downstream open reading frames (ORFs), designated B and C, respectively. The B ORFs are 1,635 bp long. Their derived amino acid sequences are 99% identical and demonstrate similar ity to the derived amino acid sequences of two genes that encode prote ins required for secretion and activation of hemolysins of Proteus mir abilis and Serratia marcescens. The C ORFs are 1,950 bp long, and thei r derived amino acid sequences are 96% identical. In Escherichia coli transformants, interruption of the hmw1C or both the hmw1B and hmw1C g enes resulted in defective processing of the hmw1A structural gene pro duct and loss of the ability of the transformants to adhere to human e pithelial cells. The precise interactions of the proteins encoded by t hese gene clusters are yet to be defined, but their elucidation may fu rther our understanding of the biology of nontypeable H. influenzae ba cteria and the interaction of these organisms with the human host.