Identification of two iron-repressed periplasmic proteins in Haemophilus influenzae.
Protein expression by Haemophilus influenzae under iron-limiting growth conditions was examined. The five type b strains and four nontypeable strains studied all expressed a new protein of about 40 kDa when deprived of iron during growth. Most strains also expressed a protein of about 31 kDa under the same growth conditions. Both the 40- and 31-kDa proteins were not expressed by cells grown in iron-replete medium. The 40- and 31-kDa proteins were not expressed in iron-deficient medium to which an excess of ferric nitrate had been added, and therefore it was concluded that their expression was iron regulated. These iron-repressed proteins were localized to the periplasmic space. The amino-terminal sequences of both proteins were determined. The N-terminal sequence of the 40-kDa protein had 81% similarity to the N terminus of Fbp, the major iron-binding protein of Neisseria gonorrhoeae and N. meningitidis. The 31-kDa protein sequence showed no homology with any known protein sequence. As no plasmids were found in the strains, it was concluded that these proteins were chromosomally encoded.
Harkness
R E
RE
Connaught Centre for Biotechnology Research, Willowdale, Ontario, Canada.
Chong
P
P
Klein
M H
MH
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism*; D001692:Biological Transport; D002451:Cell Compartmentation; D015964:Gene Expression Regulation, Bacterial; D006193:Haemophilus influenzae / Q000378:metabolism*; D007501:Iron / Q000378:metabolism*; D008969:Molecular Sequence Data; D008970:Molecular Weight; D010957:Plasmids
D001426:Bacterial Proteins; D007501:Iron