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J. Bacteriol., 08 1997, 4778-4788, Vol 179, No. 15
J Aduse-Opoku, JM Slaney, M Rangarajan, J Muir, KA Young and MA Curtis
The prpR1 gene of Porphyromonas gingivalis W50 encodes the polyprotein
precursor (PrpRI) of an extracellular arginine-specific protease. PrpRI is
organized into four distinct domains (pro, alpha, beta, and gamma) and is
processed to a heterodimeric protease (RI) which comprises the alpha and
beta components in a noncovalent association. The alpha component contains
the protease active site, whereas the beta component appears to have a role
in adherence and hemagglutination processes. DNA sequences homologous to
the coding region for the RI beta component are present at multiple loci on
the P. gingivalis chromosome and may represent a family of related genes.
In this report, we describe the cloning, sequence analysis, and
characterization of one of these homologous loci isolated in plasmid pJM7.
The 6,041-bp P. gingivalis DNA fragment in pJM7 contains a major open
reading frame of 3,291 bp with coding potential for a protein with an Mr
118,700. An internal region of the deduced sequence (V304 to N768) shows
98% identity to the beta domain of PrpRI, and the recombinant product of
pJM7 is immunoreactive with an antibody specific to the RI beta component.
The N terminus of the deduced sequence has regional similarity to TonB-
linked receptors which are frequently involved in periplasmic translocation
of hemin, iron, colicins, or vitamin B12 in other bacteria. We have
therefore designated this gene tla (TonB-linked adhesin). In contrast to
the parent strain, an isogenic mutant of P. gingivalis W50 in which the tla
was insertionally inactivated was unable to grow in medium containing low
concentrations of hemin (<2.5 mg liter(-1)), and hemin-depleted cells of
this mutant failed to respond to hemin in an agar diffusion plate assay.
These data suggest a role for this gene product in hemin acquisition and
utilization. Furthermore, the mutant produced significantly less arginine-
and lysine-specific protease activities than the parent strain, indicating
that there may be a regulatory relationship between tla and other members
of this gene family.
Copyright © 1997, American Society for Microbiology
The Tla protein of Porphyromonas gingivalis W50: a homolog of the RI protease precursor (PrpRI) is an outer membrane receptor required for growth on low levels of hemin
Department of Oral Microbiology, St. Bartholomew's and the Royal London School of Medicine and Dentistry, Queen Mary and Westfield College, England. J.Aduse@mds.qmw.ac.uk
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