Affiliation:
1. Department of Microbiology and Infectious Diseases, University of Calgary, Health Sciences Center, Calgary, Alberta, Canada T2N 4N1
Abstract
ABSTRACT
Pathogenic members of the family
Neisseriaceae
produce specific receptors facilitating iron acquisition from transferrin (Tf) and lactoferrin (Lf) of their mammalian host. Tf receptors are composed of two outer membrane proteins, Tf-binding proteins A and B (TbpA and TbpB; formerly designated Tbp1 and Tbp2, respectively). Although only a single Lf-binding protein, LbpA (formerly designated Lbp1), had previously been recognized, we recently identified additional bacterial Lf-binding proteins in the human pathogens
Neisseria meningitidis
and
Moraxella catarrhalis
and the bovine pathogen
Moraxella bovis
by a modified affinity isolation technique (R. A. Bonnah, R.-H. Yu, and A. B. Schryvers, Microb. Pathog. 19:285–297, 1995). In this report, we characterize an open reading frame (ORF) located immediately upstream of the
N. meningitidis
B16B6
lbpA
gene. Amino acid sequence comparisons of various TbpBs with the product of the translated DNA sequence from the upstream ORF suggests that the region encodes the Lf-binding protein B homolog (LbpB). The LbpB from strain B16B6 has two large stretches of negatively charged amino acids that are not present in the various transferrin receptor homologs (TbpBs). Expression of the recombinant LbpB protein as a fusion with maltose binding protein demonstrated functional Lf-binding activity. Studies with
N. meningitidis
isogenic mutants in which the
lbpA
gene and the ORF immediately upstream of
lbpA
(putative
lbpB
gene) were insertionally inactivated demonstrated that LbpA, but not LbpB, is essential for iron acquisition from Lf in vitro.
Publisher
American Society for Microbiology
Subject
Molecular Biology,Microbiology
Cited by
42 articles.
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