Ja. Ogunnariwo et Ab. Schryvers, Characterization of a novel transferrin receptor in bovine strains of Pasteurella multocida, J BACT, 183(3), 2001, pp. 890-896
Analysis of bovine respiratory isolates of Pasteurella multocida demonstrat
ed that six of nine strains tested were capable of growth dependent upon bo
vine transferrin and of specifically binding ruminant transferrins. A singl
e 82-kDa protein was affinity isolated from the P. multocida strains with i
mmobilized bovine transferrin. In contrast to what has been observed in oth
er species, binding of this protein to immobilized transferrin was specific
ally blocked by the N-lobe subfragment of bovine transferrin. A single gene
encoding the 82-kDa protein was flanked by a leucyl-tRNA synthetase gene a
nd an IS1060 element, in contrast to other species where genes encoding the
two receptor proteins (TbpB and TbpA) are found in an operonic arrangement
. A similar gene arrangement was observed in all of the receptor-positive s
trains, in spite of the observation that they belonged to different genomic
groups. Analysis of the deduced amino acid sequence of the receptor protei
n indicated that it is a member of the TonB-dependent outer membrane recept
or family, and although it is related to transferrin and lactoferrin recept
or proteins (TbpAs and LbpAs) from other species, it differs substantially
from other members of this group. Amino acid alignments suggest that the re
duced size (20 kDa smaller) of the P. multocida TbpA is primarily due to th
e absence of larger predicted external loops, Collectively these results su
ggest that P. multocida has a single, novel receptor protein (TbpA) that is
capable of efficiently mediating iron acquisition from bovine transferrin
without the involvement of a second receptor protein (TbpB).