Cloning and sequencing of the Haemophilus influenzae exbB and exbD genes

The exbB and exbD genes of Haemophilus influenzae (Hi) were cloned and sequenced. The deduced Hi ExbB and ExbD proteins possessed 27 and 28% amino-acid identity (56 and 58% relatedness) with the Escherichia coli ExbB and ExbD proteins, respectively; two proteins which function as TonB accessory proteins during biopolymer transport. Plasmid-encoded Hi exbB and exbD partially complemented an E. coli exbB/exbD mutation.