Oro-dental bacteria in various atherosclerotic arteries

Chlamydia pneumoniae DNA has been detected in at least 40% of all major arteries affected by atherosclerosis, but several other microorganisms have also been detected. In this study, diseased vessels were evaluated for the presence of the DNA of seven oro-dental bacteria and two nonoral bacteria. A polymerase chain reaction technique was employed using primer pairs based on 16S rRNA genes. Of 32 specimens tested, 10 (31.2%) were DNA positive: seven for Actinobacillus actinomycetemcomitans and three for Prevotella intermedia. The DNA was found in specimens from the aorta and the iliac, internal mammary and coronary arteries. Eleven (35.4%) of 31 specimens had been shown previously to be positive for Chlamydia pneumoniae DNA. A mixture of chlamydiae and oro-dental bacteria was found in three cases. These findings may have implications for antibiotic prophylaxis of coronary heart disease if directed solely at Chlamydia pneumoniae.

Molecular mediators of Porphyromonas gingivalis-induced T-cell apoptosis

Porphyromonas gingivalis produces virulence factors which can modify the molecular and cellular components of the host immune response. In the present work we investigated the role of specific virulence factors from P. gingivalis in the induction of apoptosis in Jurkat T cells. P. gingivalis culture supernatants mimicked the effect of butyric acid on T-cell apoptosis and this effect was associated with an increase in histone H4 acetylation. A role for proteases was excluded in experiments which demonstrated that neither protease inhibitors nor use of P. gingivalis mutants defective in protease synthesis had any effect on the stimulation of T-cell apoptosis in this system.

Recognition of the carbohydrate modifications to the RgpA protease of Porphyromonas gingivalis by periodontal patient serum IgG

Periodontal infections by Porphyromonas gingivalis are associated with a sustained systemic IgG antibody response and elevations in local antibody synthesis to this organism. One of the targets of this response is a protease, RgpAcat, which is an important virulence determinant of this organism. Recently, we demonstrated that this molecule is glycosylated and that the glycan chains are immunologically related to P. gingivalis lipopolysaccharide (LPS) (Curtis et al., Infect Immun 1999;62:3816-3823). In the present study, we examined the role of these glycan additions in the immune recognition of RgpAcat, by sera from adult periodontal patients (n = 25). Serum IgG antibody levels to P. gingivalis W50, RgpAcat and LPS and to recombinant RgpA were determined by enzyme-linked immunosorbant assay (ELISA). No correlation was observed between the antibody levels to RgpAcat from P. gingivalis and the recombinant form of this enzyme expressed in Escherichia coli. However, a strong association was found between the recognition of LPS and the wild-type enzyme (R = 0.8926; p = 0.0005). Incorporation of LPS into the ELISA led to a significant reduction (mean 25%; range 0.8-43%, SD = 15; p < 0.05) in the recognition of RgpAcat, but had no effect on the recognition of control antigens. Deglycosylation of RgpAcat led to the abolition of immune recognition by patient serum IgG, which suggests that the glycan additions to this molecule are the principal targets of the immune response. Therefore, glycosylation of the RgpAcat protease may play an important role in immune evasion by shielding the primary structure from immune recognition.

LuxS-dependent quorum sensing in Porphyromonas gingivalis modulates protease and haemagglutinin activities but is not essential for virulence

Porphyromonas gingivalis is a Gram-negative black-pigmented obligate anaerobe implicated in the aetiology of human periodontal disease. The virulence of P. gingivalis is associated with the elaboration of the cysteine proteases Arg-gingipain (Rgp) and Lys-gingipain (Kgp), which are produced at high bacterial cell densities. To determine whether quorum sensing plays a role in the regulation of Rgp and Kgp, biosensors capable of detecting either N-acylhomoserine lactone (AHLs) or the luxS-dependent autoinducer (AI-2) quorum-sensing signalling molecules in spent culture supernatants were first employed. While no AHLs could be detected, the Vibrio harveyi BB170 biosensor was activated by spent P. gingivalis W50 culture supernatants. The P. gingivalis luxS gene was cloned and demonstrated to restore AI-2 production in the Escherichia coli luxS mutant DH5alpha. Mutation of luxS abolished AI-2 production in P. gingivalis. Western blotting using antibodies raised against the recombinant protein revealed that LuxS levels increased throughout growth even though AI-2 activity was only maximally detected at the mid-exponential phase of growth and disappeared by the onset of stationary phase. Similar results were obtained with E. coli DH5alpha transformed with luxS, suggesting that AI-2 production is not limited by a lack of LuxS protein. Analysis of Rgp and Kgp protease activities revealed that the P. gingivalis luxS mutant produced around 45% less Rgp and 30% less Kgp activity than the parent strain. In addition, the luxS mutant exhibited a fourfold reduction in haemagglutinin titre. However, these reductions in virulence determinant levels were insufficient to attenuate the luxS mutant in a murine lesion model of P. gingivalis infection.

Cysteine proteases of Porphyromonas gingivalis

The cysteine proteases of Porphyromonas gingivalis are extracellular products of an important etiological agent in periodontal diseases. Many of the in vitro actions of these enzymes are consistent with the observed deregulated inflammatory and immune features of the disease. They are significant targets of the immune responses of affected individuals and are viewed by some as potential molecular targets for therapeutic approaches to these diseases. Furthermore, they appear to represent a complex group of genes and protein products whose transcriptional and translational control and maturation pathways may have a broader relevance to virulence determinants of other persistent bacterial pathogens of human mucosal surfaces. As a result, the genetics, chemistry, and virulence-related properties of the cysteine proteases of P. gingivalis have been the focus of much research effort over the last ten years. In this review, we describe some of the progress in their molecular characterization and how their putative biological roles, in relation to the in vivo growth and survival strategies of P. gingivalis, may also contribute to the periodontal disease process.

Generation of lys-gingipain protease activity in Porphyromonas gingivalis W50 is independent of Arg-gingipain protease activities

Porphyromonas gingivalis, a black-pigmenting anaerobe implicated in the aetiology of periodontal disease, contains two loci, rgpA and rgpB, encoding the extracellular Arg-X specific proteases (RGPs, Arg-gingipains), and kgp, which encodes a Lys-X specific protease (KGP, Lys-gingipain). The rgpA and kgp genes encode polyproteins comprising pro-peptide and catalytic domain with large N- and C-terminal extensions which require proteolytic processing at several Arg and Lys residues to generate mature enzymes. The product of rgpB contains only a pro-peptide and the catalytic domain which requires processing at an Arg residue to generate active enzyme. An rgpA rgpB double mutant (E8) of P. gingivalis was constructed to study the role of RGPs in the processing of KGP. A kgp mutant (K1A) was also studied to investigate the role of KGP in the generation of RGPs. E8 was stable in the absence of the antibiotics tetracycline and clindamycin (selection markers for rgpA and rgpB, respectively) and exhibited the same pigmentation, colony morphology and identical growth rates to the parent W50 strain in the absence of antibiotics, in both complex and chemically defined media. The KGP activity of E8, grown in the absence of tetracycline, in whole cultures and in culture supernatants (up to 6 d) was identical to levels in W50. However, in the presence of tetracycline in the growth medium, the level of KGP was reduced to 50% of levels present in whole cultures of W50. Since tetracycline had no effect on RGP or KGP activity when incorporated into assay buffer, this effect is most likely to be on the synthesis of Kgp polypeptide. K1A was also stable in the absence of antibiotics but was unable to pigment, and remained straw-coloured throughout growth. RGP activity in whole cultures of K1A was identical to levels in W50, but RGP activity in 6 d culture supernatants was reduced to 50% of levels present in W50. Thus, although KGP is not required for generation of RGP activity from RgpA and RgpB polypeptides, its absence affects the release/transport of RGP into culture supernatant.

Identification of ragAB as a temperature-regulated operon of Porphyromonas gingivalis W50 using differential display of randomly primed RNA

Porphyromonas gingivalis is a gram-negative, black-pigmented anaerobe that has been associated with advanced periodontal disease. The genome of P. gingivalis has the potential to produce a number of virulence determinants including proteases, hemagglutinins, hemolysin, invasion-associated proteins, and products of the pathogenicity island ragAB; however, little is known about how their expression is controlled. Periodontal pockets experience a higher temperature during inflammation, and this elevated temperature may influence the pathogenicity of P. gingivalis by changing its patterns of gene expression. In this study, RNA has been isolated from cells of P. gingivalis grown to steady state at temperatures of 37, 39, and 41 degrees C under hemin excess conditions (pH 7.0) in a chemostat. The RNA was subjected to PCR amplification following reverse transcription, using various combinations of randomly selected oligonucleotide primers. Reproducible RNA fingerprints have been obtained; however, differences were demonstrated in the RNA profiles of cells grown at the three temperatures, indicating differences in gene expression. Several PCR fragments were isolated that appeared to represent temperature-regulated genes. The nucleotide sequence of one of these has been identified as part of the ragAB locus, which codes for both a 55-kDa immunodominant antigen (RagB) and a homologue of the family of TonB-linked outer membrane receptors (RagA). These data indicate that expression of ragAB may be modulated in response to changes in temperature and that this may suggest a mechanism of evading the host response in the inflamed periodontal pocket.

Molecular genetics and nomenclature of proteases of Porphyromonas gingivalis

The strategies used by bacterial pathogens to establish and maintain themselves in the host represent one of the fundamental aspects of microbial pathogenesis. Characterization of these strategies and the underlying molecular machinery offers new opportunities both to our understanding of how organisms cause disease in susceptible individuals and to the development of novel therapeutic measures designed to undermine or interfere with these determinants of successful survival. With respect to the microbial aetiology of the periodontal diseases, a growing body of evidence suggests that the proteolytic enzymes of Porphyromonas gingivalis represent key survival and, by extrapolation, virulence determinants of this periodontal bacterium. This in turn has led to international efforts to characterize these enzymes at the gene and protein level. Approximately 20 protease genes of P. gingivalis with different names and accession numbers have been deposited in the gene databases and a correspondingly heterogeneous nomenclature system is employed for the products of these genes in the literature. However, it is evident, through comparison of these gene sequences and through gene inactivation studies, that the genetic structure of the proteases of this organism, particularly those with specificity for arginyl and lysyl peptide bonds, is less complicated than originally thought. The major extracellular and surface associated arginine specific protease activity is encoded by 2 genes which we recommend be designated rgpA and rgpB (arg-gingipains A & B). Similarly we recommend that the gene encoding the major lysine specific protease activity is designated kgp (lys-gingipain). These three genes, which account for all the extracellular/surface arginine and lysine protease activity in P. gingivalis, belong to a family of sequence-related proteases and haemagglutinins.

The rag locus of Porphyromonas gingivalis: a novel pathogenicity island

Previous studies in our laboratories of the serum IgG antibody response of periodontal patients have demonstrated the presence of an immunodominant surface antigen (Mr 55 kDa) in the outer membrane of Porphyromonas gingivalis W50. Genetic analysis of this antigen revealed that the corresponding gene forms part of a small operon which may have arisen via horizontal gene transfer into the genome of this strain. On the basis of sequence homology, the 55 kDa antigen (RagB) and the product of a cotranscribed gene (RagA) may act in concert at the surface of the bacterium to facilitate active transport, mediated through the periplasmic spanning protein, TonB, or form part of a signal transduction system in this organism. The rag locus is present in only a proportion of P. gingivalis laboratory strains and clinical isolates. Analysis of the distribution of ragB in subgingival samples by PCR demonstrated that rag+ P. gingivalis are more frequently detected in deep periodontal pockets than shallow sites in periodontal patients. These findings indicate that the rag genes may influence the virulence potential of P. gingivalis strains which harbour this locus and may thus be considered a novel pathogenicity island. Furthermore, horizontal gene transfer between organisms in subgingival plaque may represent a significant force in the evolution of these bacteria with ramifications for both diagnosis and targeted treatment of periodontal disease.

Variable carbohydrate modifications to the catalytic chains of the RgpA and RgpB proteases of Porphyromonas gingivalis W50

Proteases of Porphyromonas gingivalis are considered to be important virulence determinants of this periodontal bacterium. Several biochemical isoforms of arginine-specific proteases are derived from rgpA and rgpB. HRgpA is a heterodimer composed of the catalytic alpha chain noncovalently associated with a beta adhesin chain derived from the C terminus of the initial full-length translation product. The catalytic alpha chain is also present as a monomer (RgpA) either free in solution or associated with membranes. rgpB lacks the coding region for the adhesin domain present in rgpA and yields only monomeric forms (RgpB) which again may be soluble or membrane associated. In this study, the catalytic chains of this unusual group of enzymes are shown to be differentially modified by the posttranslational addition of carbohydrate. A monoclonal antibody (MAb 1B5) raised to the monomeric RgpA did not react with the corresponding recombinant RgpA alpha chain expressed in Escherichia coli but was immunoreactive with P. gingivalis lipopolysaccharide. MAb 1B5 also reacted with the membrane-associated forms of RgpA and RgpB but not with the heterodimeric HRgpA and the soluble form of RgpB. RgpA treated with denaturants was capable of binding to MAb 1B5 whereas treatment with periodate abolished this binding, suggesting the presence of carbohydrate residues within the epitope. Chemical deglycosylation abolished immunoreactivity with MAb 1B5 and caused a approximately 30% reduction in the size of the membrane-associated enzymes. Monosaccharide analysis of HRgpA and RgpA demonstrated 2.1 and 14.4%, respectively, carbohydrate by weight of protein. Furthermore, distinct differences were detected in their monosaccharide compositions, indicating that these protease isoforms are modified not only to different extents but also with different sugars. The variable nature of these additions may have a significant effect on the structure, stability, and immune recognition of these protease glycoproteins.

Effect of temperature on growth, hemagglutination, and protease activity of Porphyromonas gingivalis

Bacteria persisting in periodontal pockets are exposed to elevated temperatures during periods of inflammation. Temperature is an environmental factor that can modulate gene expression. Consequently, in the present study we examined the effect of temperature on the expression of virulence determinants by the periodontopathogen, Porphyromonas gingivalis. P. gingivalis W50 was grown in a complex medium under hemin excess at pH 7.0 and at a constant temperature of either 37, 39, or 41 degrees C; cultures were monitored for protease and hemagglutinin activity. P. gingivalis grew well at all three temperatures. An increase in growth temperature from 37 to 39 degrees C resulted in a 65% reduction in both total arginine- and lysine-specific activities (P < 0.01). A further rise in growth temperature to 41 degrees C led to even greater reductions in arginine-specific (82%; P < 0.001) and lysine-specific (73%; P < 0. 01) activities. These reductions were also associated with an altered distribution of individual arginine-specific enzyme isoforms. At 41 degrees C, there was a disproportionate reduction in the level of the heterodimeric RI protease, which also contains adhesin domains. The reduction also correlated with a markedly diminished hemagglutination activity of cells, especially in those grown at 41 degrees C, and a reduced immunoreactivity with a monoclonal antibody which recognizes gene products involved in hemagglutination. Thus, as the environmental temperature increased, P. gingivalis adopted a less aggressive phenotype, while retaining cell population levels. The coordinate down-regulation of virulence gene expression in response to an environmental cue linked to the intensity of the host inflammatory response is consistent with the clinically observed cyclical nature of disease progression in periodontal diseases.

A 55-kilodalton immunodominant antigen of Porphyromonas gingivalis W50 has arisen via horizontal gene transfer

A 55-kDa outer membrane protein of Porphyromonas gingivalis W50 is a significant target of the serum immunoglobulin G antibody response of periodontal disease patients and hence may play an important role in host-bacterium interactions in periodontal disease. The gene encoding the 55-kDa antigen (ragB, for receptor antigen B) was isolated on a 9.5-kb partial Sau3AI fragment of P. gingivalis W50 chromosomal DNA in pUC18 by immunoscreening with a monoclonal antibody to this antigen. The 1.6-kb open reading frame (ORF) encoding RagB was located via subcloning and nested-deletion analysis. Sequence analysis demonstrated the presence of an upstream 3.1-kb ORF (ragA) which is cotranscribed with ragB. A number of genetic characteristics suggest that the ragAB locus was acquired by a horizontal gene transfer event. These include a significantly reduced G+C content relative to that of the P. gingivalis chromosome (42 versus 48%) and the presence of mobility elements flanking this locus in P. gingivalis W50. Furthermore, Southern blotting and PCR analyses showed a restricted distribution of this locus in laboratory and clinical isolates of this bacterium. The association of ragAB+ P. gingivalis with clinical status was examined by PCR analysis of subgingival samples. ragAB+ was not detected in P. gingivalis-positive shallow pockets from periodontal disease patients but was present in 36% of the P. gingivalis-positive samples from deep pockets. These data suggest that the ragAB locus was acquired by certain P. gingivalis strains via horizontal gene transfer and that the acquisition of this locus may facilitate the survival of these strains at sites of periodontal destruction.

Maturation of the arginine-specific proteases of Porphyromonas gingivalis W50 is dependent on a functional prR2 protease gene

The prpR1 of Porphyromonas gingivalis codes for three distinct enzymes with specificity for arginyl peptide bonds termed RI, RIA, and RIB. These three isoforms comprise the majority of the extracellular, arginine-specific protease activity in P. gingivalis W50. RI is a heterodimer in which the catalytic alpha chain is noncovalently associated with a second chain involved in adherence phenomena. RIA and RIB are both monomeric species. RIA represents the free alpha chain, and RIB is a highly posttranslationally modified form of the alpha chain which is exclusively vesicle or membrane associated and migrates as a diffuse band on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. In previous studies, insertional inactivation of the prpR1 demonstrated that arginine-specific protease activity can also arise from a closely related second gene, prR2. In the present work, the prR2 was insertionally inactivated in P. gingivalis W50 in order to establish the contribution of this locus to the arginine-specific protease activity of this periodontal bacterium. Loss of prR2 function had several effects on prpR1-derived enzymes. First, the total Arg-X activity was reduced by approximately 50% relative to that of the parent strain. The reduction in total activity was a consequence of decreased concentrations of the monomeric enzymes derived from the prpR1, while the heterodimeric enzyme, RI, was unaffected by this mutation. Second, the chromatographic behavior of both the soluble and vesicle- or membrane-associated monomeric enzymes was radically different from the behavior of RIA and RIB from the parent strain. Finally, the vesicle- or membrane-associated enzyme in the prR2 mutant strain lacked the extensive posttranslational additions which are found on RIB in P. gingivalis W50. These data suggest that the product(s) of the prR2 plays a significant role in the maturation pathway of prpR1-derived enzymes, and this may contribute to the coconservation of these two genes in P. gingivalis.

Natural variation within the principal arginine-specific protease gene, prpR1, of Porphyromonas gingivalis

RI, one of the major extracellular arginine-specific proteases of Porphyromonas gingivalis is a heterodimer composed of catalytic (alpha) and adhesin (beta) chains, encoded by the gene prpR1. The distribution of prpR1 and its variation within 43 isolates of P. gingivalis was determined. Chromosomal DNA was digested with Sma I and probed with a 32P-labeled DNA fragment from within the coding region for the alpha component of P. gingivalis W50. All isolates gave the expected 3.2 kb band, corresponding to the coding region for the alpha and beta components. The presence of a second locus (prR2) homologous to the alpha region of prpR1 was also detected. The 1.7-kb alpha coding region of prpR1 was amplified for subsequent restriction analysis. Following Taq I restriction all isolates gave identical patterns. With Rsa I, the majority of isolates (77%) could be placed into a single group. In conclusion, the prpR1 and prR2 loci are maintained in natural populations of P. gingivalis, and only minor polymorphism is detectable within the catalytic domain.

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

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.

The prpR1 and prR2 arginine-specific protease genes of Porphyromonas gingivalis W50 produce five biochemically distinct enzymes

The arginine-specific protease activity of Porphyromonas gingivalis is considered to be an important factor in the pathogenic potential of this organism in destructive periodontal disease. Multiple forms of closely related Arg-x proteases are present in the culture supernatants of P. gingivalis W50. RI is a heterodimer (alpha/beta) in which the catalytic alpha chain is associated with a second beta chain which functions as a haemagglutinin. RIA is a single-chain enzyme (alpha) and RIB is a highly post-translationally lipid-modified enzyme (LPS-alpha) with reduced solubility compared to the other two forms. The N-terminal sequence of the alpha chain of all three forms is identical, suggesting that all these enzymes may arise by differential processing of the prpR1 (protease polyprotein for RI). In the present study we constructed a prpR1- strain of P. gingivalis W50 by insertional gene inactivation and characterized the residual extracellular Arg-x protease activity of the resulting mutant. Loss of prpR1 expression led to the abolition of RI, RIA and RIB but the total Arg-x activity in the supernatant of this strain was reduced by only c. 66%. The remaining activity was composed of two novel forms of Arg-x protease (RIIA and RIIB) which appeared to be structurally and kinetically almost identical to RIA and RIB, respectively, except for two amino acid differences in the N-terminus at position 8 (Q-->E) and position 17 (A-->P) and with respect to their stability to high pH. Confirmation that RIIA and RIIB are the products of a homologous locus (prR2) was obtained by cloning and sequencing the prR2 which showed the predicted substitutions in the deduced translation. These data indicate that RI, RIA and RIB are produced by prpR1 expression and a maturation pathway which can give rise to a dimer and an unmodified- or LPS-modified catalytic monomer. Furthermore, RIIA and RIIB, the products of prR2, are exported into the culture supernatant in the absence of prpR1 expression and these forms may also contribute to the pathogenic potential of this organism in destructive disease.

Characterization of an adherence and antigenic determinant of the ArgI protease of Porphyromonas gingivalis which is present on multiple gene products

This study was performed to characterize the antigen(s) recognized by a panel of monoclonal antibodies (MAbs) produced to be specific for Porphyromonas gingivalis whole cells which we had previously shown to bind to epitopes recognized by sera from periodontitis patients. Preliminary data had suggested that the arginine-specific proteases of P. gingivalis (ArgI, ArgIA, and ArgIB) contained the antigenic determinants of four of these antibodies (MAbs 1A1, 2B/H9, 7D5, and 3B1). The location of the binding sites was examined with purified P. gingivalis enzymes and recombinant regions of the ArgI polyprotein expressed by subclones of the prpR1 gene in Escherichia coli XL-1 Blue cells. All four antibodies were reactive with protein determinants within the beta subunit, a hemagglutinin and/or adhesin component, of the ArgI dimer. MAb 1A1 strongly inhibited the agglutination of human erythrocytes by P. gingivalis W50 culture supernatant, suggesting that the binding site for this antibody contains residues which are critical for the interaction with the erythrocyte surface. The determinant for MAb 1A1 was examined further by construction of a set of truncated forms of the beta component expressed as fusion proteins with glutathione S-transferase at the N terminus. Analysis of these constructs mapped the binding site for MAb 1A1 to PrpRI residues G-907 to T-931, GVSPKVCKDV TVEGSNEFAP VQNLT. Western blot (immunoblot) analysis of P. gingivalis whole-cell proteins demonstrated that MAb 1A1 reacts with several proteins in the Mr range of 20,000 to 120,000. Furthermore, an oligonucleotide probe corresponding to the coding sequence for the region of the ArgI beta component containing the MAb 1A1 binding site hybridized to multiple bands on genomic digests of P. gingivalis DNA. These data indicate that the MAb 1A1 epitope may be a component of a binding domain common to multiple gene products of this organism and may thus represent a functionally important target of the host's specific immune response to P. gingivalis in periodontal disease.

Characterization, genetic analysis, and expression of a protease antigen (PrpRI) of Porphyromonas gingivalis W50

Previous studies of the serum immunoglobulin G antibody response of periodontal patients have demonstrated significant reactivity to a cell surface or extracellular arginine-specific protease of Porphyromonas gingivalis which migrates as an approximately 50-kDa band on sodium dodecyl sulfate-polyacrylamide gels. In the present report, two forms of the enzyme (ArgI and ArgIA) with this electrophoretic behavior were isolated. ArgI is a heterodimer of alpha and beta subunits, and ArgIA is a monomer composed of the catalytically active alpha component alone. The gene encoding ArgI (prpR1 encoding protease polyprotein ArgI) was cloned from Sau3AI digests of P. gingivalis W50 DNA into pUC18. Sequence analysis demonstrated that the alpha and beta components are contiguous on the initial translation product and are flanked by large N- and C-terminal extensions. prpR1 is 97.5% identical to the rgp-1 gene from P. gingivalis H66. prpR1 expression in Escherichia coli demonstrated the presence of an internal transcription-translation initiation site which could permit independent expression of different regions of the polyprotein. Immunochemical analysis of P. gingivalis mid-logarithmic-phase cultures suggested that the processing of PrpRI may be closely coupled to its synthesis, with only the final stages taking place at the cell surface. Southern hybridization studies demonstrated that the prpR1 gene is widely distributed in other P. gingivalis strains and that a second homologous locus to the alpha component and at least two other homologous loci to the beta component are present on the P. gingivalis chromosome. These data indicate that the ArgI protease of P. gingivalis is a member of a family of sequence-related gene products which may share both functional and antigenic properties.

The xylose isomerase-encoding gene (xylA) of Clostridium thermosaccharolyticum: cloning, sequencing and phylogeny of XylA enzymes

The xylose isomerase (XylA)-encoding gene (xylA) of the thermophilic anaerobic bacterium, Clostridium thermosaccharolyticum NCIB 9385, was cloned as a 4.0-kb DNA fragment by complementation of the Escherichia coli xylA mutant strain, DS941. The open reading frame of 1317 bp encoded a protein of 439 amino acids (aa), with a calculated M(r) of 50,236. The gene was preceeded by a typical clostridial Shine-Dalgarno sequence, and was expressed constitutively in the cloning host. Downstream, the clone appeared to carry a xylB gene (encoding xylulokinase) in the same orientation as xylA. Comparison of the deduced aa sequence of the C. thermosaccharolyticum XylA with 18 other XylA showed that this family of proteins was separated into two clusters, one comprising proteins from organisms with G + C-rich DNA, and the other proteins from organisms with a lower G + C composition. Within the second cluster, the XylA of C. thermosaccharolyticum was most closely related to the enzymes from C. thermosulfurogenes (Thermoanaerobacterium thermosulfurigenes) and C. thermohydrosulfuricum (93 and 84% identity, respectively). Analysis of the aligned sequences indicated two signatures (VXW[GP]GREG[YSTA]E and [LIVM]EPKPX]EQ]P) which may be useful in isolation of novel XylA.

A binding protein-dependent transport system in Streptococcus mutans responsible for multiple sugar metabolism

An 11-kilobase gene region of Streptococcus mutans has been identified which contains eight contiguous genes involved with the uptake and metabolism of multiple sugars (the msm system). Sequence analysis of this region indicates that several of these genes specify proteins with strong homology to components of periplasmic binding protein-dependent transport systems of Gram-negative bacteria. Additionally, this operon is controlled by a regulatory gene (msmR) that acts as a positive effector. The proteins specified by the structural genes of the msm operon include alpha-galactosidase (aga), a "periplasmic-like" sugar-binding protein (msmE), two membrane proteins (msmF, msmG), sucrose phosphorylase (gtfA), an ATP-binding protein (msmK), and dextran glucosidase (dexB). Insertional inactivation of each of these genes along with uptake data indicate that this system is responsible for the uptake of melibiose, raffinose, and isomaltotriose and the metabolism of melibiose, sucrose, and isomaltosaccharides.

Chromosomal deletions in melibiose-negative isolates of Streptococcus mutans

Isolates from a collection of phenotypically melibiose-negative (Mel-) Streptococcus mutans from widely-scattered geographical locations were examined and found to lack the activities of the enzymes alpha-galactosidase and alpha-glucosidase, in addition to being unable to transport melibiose. Cloned fragments of S. mutans DNA from the region of the chromosome carrying the genes for alpha-galactosidase (aga), sucrose phosphorylase (gtfA), and dextran glucosidase (dexB), as well as the genes encoding components of the binding-protein-dependent uptake system for raffinose and melibiose, were used in hybridization studies for investigation of the genetic basis of the Mel-phenotype. A region of at least 12 kilobases, containing all the above genes, was found to be deleted from the chromosome of the Mel- strains. It appears that this region of the chromosome is not essential for survival of S. mutants in the oral cavity. The reason for the frequent occurrence of deletions, as opposed to other forms of mutational events, is unknown.