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PubMed1989

Characterization of salivary alpha-amylase binding to Streptococcus sanguis.

The purpose of this study was to identify the major salivary components which interact with oral bacteria and to determine the mechanism(s) responsible for their binding to the bacterial surface. Strains of Streptococcus sanguis, Streptococcus mitis, Streptococcus mutans, and Actinomyces viscosus were incubated for 2 h in freshly collected human submandibular-sublingual saliva (HSMSL) or parotid saliva (HPS), and bound salivary components were eluted with 2% sodium dodecyl sulfate. By sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western transfer, alpha-amylase (EC 3.2.1.1) was the prominent salivary component eluted from S. sanguis. Studies with 125I-labeled HSMSL or 125I-labeled HPS also demonstrated a component with an electrophoretic mobility identical to that of alpha-amylase which bound to S. sanguis. Purified alpha-amylase from human parotid saliva was radiolabeled and found to bind to strains of S. sanguis genotypes 1 and 3 and S. mitis genotype 2, but not to strains of other species of oral bacteria. Binding of [125I]alpha-amylase to streptococci was saturable, calcium independent, and inhibitable by excess unlabeled alpha-amylases from a variety of sources, but not by secretory immunoglobulin A and the proline-rich glycoprotein from HPS. Reduced and alkylated alpha-amylase lost enzymatic and bacterial binding activities. Binding was inhibited by incubation with maltotriose, maltooligosaccharides, limit dextrins, and starch.

Adult↗
PubMed1991

Adherence of Porphyromonas (Bacteroides) gingivalis to Streptococcus sanguis in vitro.

Intergeneric bacterial adherence is responsible for the complexity of the microbiota in human dental plaque and is believed to enable some extraneous bacteria to initially colonize the human oral cavity. Some current evidence indicates that Streptococcus sanguis, an early colonizer of teeth, enhances subsequent colonization by Porphyromonas (Bacteroides) gingivalis, a bacterium associated with advanced adult periodontitis. In this study, selected strains of P. gingivalis and S. sanguis were tested for their adherence activities in vitro. A differential filtration assay was devised in which one member of the test pair was radiolabeled. Heterogeneous aggregates that formed in mixed suspensions were collected on polycarbonate filters (8-microns pore size) and were washed free of individual bacteria and small homologous clumps. P. gingivalis 381, W50, JKG7, and 33277 adhered to S. sanguis G9B, M5, Challis 6, and 38. P. gingivalis A7A1-28 did not adhere well to S. sanguis under these conditions. More precise measurements of intergeneric adherence were obtained with an alternative assay with radiolabeled P. gingivalis and an artificial dental plaque composed of S. sanguis coupled to cyanogen bromide-activated agarose beads. CNBr-agarose was selected as the supporting matrix for the plaque because it was uniformly and permanently coated with S. sanguis and because P. gingivalis had negligible adherence activity for streptococcus-free beads. P. gingivalis W50 grown to the early stationary phase adhered to S. sanguis-coated beads in higher numbers than either midlogarithmic- or late-stationary-phase cells. Intergeneric adherence was not inhibited or reversed by the presence of lactose or other monosaccharides or disaccharides. Pretreatment of either bacterium with trypsin or proteinase K reduced subsequent adherence by 86 to 100%. Neuraminidase treatment of P. gingivalis caused 98% reduction of adherence, whereas similar treatment of S. sanguis caused only a 2% loss. Preincubation of P. gingivalis at 60 degrees C for 30 min decreased subsequent adherence to S. sanguis-coated beads by 94%. Adherence was reduced by 96% when bacteria were assayed while suspended in human whole saliva or when pretreated with saliva and subsequently assayed in buffer. The concentration of whole human saliva required to inhibit 50% adherence in this assay was 23 micrograms per ml (1:200 dilution). Suspension of the bacteria in normal rabbit serum resulted in 94% inhibition of adherence. These data indicate that saliva and serum may be important host defense factors for controlling Porphyromonas-Streptococcus adherence.

Adhesins, Bacterial↗
PubMed1991

Sequence and structural analysis of surface protein antigen I/II (SpaA) of Streptococcus sobrinus.

Streptococcal antigen I/II or the surface protein antigen A (SpaA) of Streptococcus sobrinus is an adhesin which mediates binding of the organism to tooth surfaces. The complete sequence of the gene which encodes SpaA has been determined. The gene consists of 4,584 bp and encodes a protein of 1,528 amino acid residues. The deduced amino acid sequence shows extensive homology with those of the cell surface adhesins from Streptococcus mutans serotypes c and f and from Streptococcus sanguis. Structural analysis of the N-terminal region (residues 50 to 550), which is rich in alanine and includes four tandem repeats of an 82-residue sequence, suggests that it adopts an alpha-helical coiled-coil conformation. Cell surface hydrophobicity may be associated with this region. The C-terminal region is more conserved and includes two tandem repeats of a 39-residue proline-rich sequence. A further proline-rich sequence in this region is predicted to span the cell wall. Although a hydrophobic sequence is present in the C-terminal region, it appears to be too short to span the cell membrane. Anchoring of SpaA in the cell membrane may therefore require some form of posttranslational modification or association with another membrane protein.

Adhesins, Bacterial↗
PubMed1991

Delineation of a segment of adsorbed salivary acidic proline-rich proteins which promotes adhesion of Streptococcus gordonii to apatitic surfaces.

Cells of several strains of Streptococcus gordonii attached in much higher numbers to experimental pellicles formed from samples of submandibular or parotid saliva on hydroxyapatite (HA) beads than to buffer controls. The nature of the salivary components responsible were investigated by preparing experimental pellicles from chromatographic fractions of submandibular saliva obtained from Trisacryl GF 2000M columns. Adhesion of S. gordonii Blackburn was promoted by two groups of fractions. The adhesion-promoting activity in the first group of fractions was associated with the family of acidic proline-rich proteins (PRPs), while that of the second group is as yet unidentified. Experimental pellicles prepared by treating HA with 2 micrograms of pure 150-amino-acid-residue PRPs (PRP-1, PRP-2, and PIF-s) promoted adhesion of S. gordonii Blackburn cells to an extent comparable to that obtained with unfractionated saliva. However, pellicles prepared from a 106-residue PRP (PRP-3) were significantly less effective, and those prepared from the amino-terminal tryptic peptide (residues 1 to 30) of the PRP and the salivary phosphoprotein statherin were completely ineffective in promoting adhesion. Although adhesion of several strains of S. gordonii was promoted by adsorbed PRP-1, the adhesion of several strains of Streptococcus sanguis or Streptococcus oralis was either not affected or only weakly enhanced by this protein. S. gordonii cells bound avidly to PRPs adsorbed onto HA beads, but the streptococci did not appear to bind PRPs in solution, since concentrations of PRP as high as 200 micrograms/ml did not inhibit binding of bacterial cells to pellicles prepared from pure PRP. S. gordonii cells also attached well to PRP or a synthetic decapeptide representing residues 142 to 150 of the PRP when the peptide was linked to agarose beads. Studies with a series of synthetic decapeptides indicated that the minimal segment of PRP which promoted high levels of S. gordonii adhesion was the carboxy-terminal dipeptide Pro-Gln (residues 149 and 150).

Adsorption↗
PubMed1993

Cloning and expression of the multiple sugar metabolism (msm) operon of Streptococcus mutans in heterologous streptococcal hosts.

The multiple sugar metabolism (msm) operon of Streptococcus mutans is responsible for the uptake and metabolism of a variety of sugars. In order to further characterize the substrate specificities of the transport system, a 12-kb region of DNA containing the entire msm operon was cloned, via a novel two-step integration strategy, into the chromosomes of two heterologous streptococcal strains, Streptococcus gordonii Challis and Streptococcus anginosus Is57, as well as the chromosome of a natural isolate of S. mutans with a deletion of the msm region. These strains are unable to transport or ferment melibiose, raffinose, or isomaltosaccharides, but the newly constructed recombinants gained the ability to ferment all of these sugars. The S. gordonii Challis construct containing msm was shown to transport radiolabelled melibiose, raffinose, isomaltotriose, and isomaltotetraose, and the transport function was also subjected to induction by raffinose, an inducer of the msm operon in S. mutans. The results confirm the role of the msm operon in the transport and metabolism of melibiose, raffinose, and isomaltosaccharides.

Biological Transport↗
PubMed1996

Defining antibody targets in Streptococcus oralis infection.

Immunoblotting of sera from 12 neutropenic patients with Streptococcus oralis septicemia and 18 patients with endocarditis due to viridans group streptococci revealed immunodominant S. oralis antigens at 85 and 180 kDa. The former cross-reacted with a mouse monoclonal antibody to hsp90. The latter was identified by sequencing positive clones obtained by screening a genomic expression library of S. oralis with pooled sera from patients who had been infected with S. oralis. Antibody eluted from one of these clones reacted with the 180-kDa antigen of S. oralis. Southern blotting confirmed the origin of the clone from S. oralis. The derived amino acid sequence showed 76.2% homology with the PAc protein precursor of Streptococcus mutans and 73.8% homology with the SpaA protein precursor of Streptococcus sobrinus. Epitope mapping of the derived amino acid sequence with sera from patients with viridans group streptococcal endocarditis delineated nine epitopes. Peptides 1 (TMYPNRQPGSGWDSS) and 2 (WYSLNGKIRAVDVPK), representing two of these epitopes, and peptide 3 (YEVEKPLEPAPVAPS), representing the repeat proline region, were synthesized. These three peptides were used to screen a phage antibody display library derived from a patient who had recovered from S. oralis infection. Two of the human recombinant antibodies produced (SORAL 3 and SORAL 4 against peptide 3) and a human recombinant antibody (B3.7) against the conserved epitope (LKVIRK) of hsp90 gave statistically significant protection, compared with control groups, in a mouse model of lethal S. oralis infection.

Amino Acid Sequence↗
PubMed1997

Role of putative virulence factors of Streptococcus pyogenes in mouse models of long-term throat colonization and pneumonia.

To investigate the role of putative virulence factors of Streptococcus pyogenes (group A streptococcus; GAS) in causing disease, we introduced specific mutations in GAS strain B514, a natural mouse pathogen, and tested the mutant strains in two models of infection. To study late stages of disease, we used our previously described mouse model (C3HeB/FeJ mice) in which pneumonia and systemic spread of the streptococcus follow intratracheal inoculation. To study the early stages of disease, we report here a model of long-term (at least 21 days) throat colonization following intranasal inoculation of C57BL/10SnJ mice. When the three emm family genes of GAS strain B514-Sm were deleted, the mutant showed no significant difference from the wild type in induction of long-term throat colonization or pneumonia. We inactivated the scpA gene, which encodes a complement C5a peptidase, by insertion of a nonreplicative plasmid and found no significant difference from the wild type in the incidence of throat colonization. However, there was a small but statistically significant decrease in the incidence of pneumonia caused by the scpA mutant. Finally, we demonstrated a very important effect of the hyaluronic acid capsule in both models. Following intranasal inoculation of mice with a mutant in which a nonreplicative plasmid was inserted into the hasA gene, which encodes hyaluronate synthase, we found that all bacteria recovered from the throats of the mice were encapsulated revertants. Following intratracheal inoculation with the hasA mutant, the incidence of pneumonia within 72 h was significantly reduced from that of the control strain (P = 0.006). These results indicate that the hyaluronic acid capsule of S. pyogenes B514 confers an important selective advantage for survival of the bacteria in the upper respiratory tract and is also an important determinant in induction of pneumonia in our model system.

Adhesins, Bacterial↗
PubMed1997

Comparison of the sequences and functions of Streptococcus equi M-like proteins SeM and SzPSe.

Streptococcus equi (Streptococcus equi subsp. equi), a Lancefield group C streptococcus, causes strangles, a highly contagious purulent lymphadenitis and pharyngitis of members of the family Equidae. The antiphagocytic 58-kDa M-like protein SeM is a major virulence factor and protective antigen. The amino acid sequence and structure of SeM has been determined and compared to that of a second, 40-kDa M-like protein (SzPSe) of S. equi and to those of other streptococcal proteins. Both SeM and SzPSe are mainly alpha-helical fibrillar molecules with no homology other than that between their signal and membrane anchor sequences and are only distantly related to other streptococcal M and M-like proteins. The sequence of SzPSe indicates that it is an allele of SzP that encodes the variable protective M-like and typing antigens of S. zooepidemicus (S. equi subsp. zooepidemicus). SeM is opsonogenic for S. equi but not for the closely related S. zooepidemicus, whereas SzPSe is strongly opsonogenic for S. zooepidemicus but not for S. equi. Both proteins bind equine fibrinogen. SeM and SzPSe proteins from temporally and geographically separated isolates of S. equi are identical in size. The results taken together support previous evidence that S. equi is a clonal pathogen originating from an ancestral strain of S. zooepidemicus. We postulate that acquisition of SeM synthesis was a key element in the success of the clone because of its effect in enhancing resistance to phagocytosis and because protective immunity entails a requirement for SeM-specific antibody.

Amino Acid Sequence↗
PubMed1999

Purification and cloning of a streptokinase from Streptococcus uberis.

A bovine plasminogen activator was purified from the culture supernatant of the bovine pathogen Streptococcus uberis NCTC 3858. After the final reverse-phase high-performance liquid chromatography step a single protein with a molecular mass of 32 kDa was detected in the active fraction. A partial peptide map was established, and degenerate primers were designed and used for amplification of fragments of the gene encoding the activator. Inverse PCR was subsequently used for obtaining the full-length gene. The S. uberis plasminogen activator gene (skc) encodes a protein consisting of 286 amino acids including a signal peptide of 25 amino acids. In an amino acid sequence comparison the cloned activator showed an identity of approximately 26% to the streptokinases isolated from Streptococcus equisimilis and Streptococcus pyogenes. Interestingly, the activator from S. uberis was found to lack the C-terminal domain possessed by the streptokinase from S. equisimilis. This is apparently a general feature of the streptokinases of this species; biochemical and genetic analysis of 10 additional strains of S. uberis revealed that 9 of these were highly similar to strain NCTC 3858. Sequencing of the skc gene from three of these strains indicated that the amino acid sequence of the protein is highly conserved within the species.

Amino Acid Sequence↗
PubMed1999

Surface expression of a protective recombinant pertussis toxin S1 subunit fragment in Streptococcus gordonii.

In this study, the expression of the Bordetella pertussis S1 subunit was tested in Streptococcus gordonii, a commensal oral bacterium which has the potential to be a live oral vaccine vehicle. The DNA fragment encoding the N-terminal 179 amino acids of the S1 subunit was ligated into the middle part of spaP, the surface protein antigen P1 gene originating from Streptococcus mutans. The resulting construct, carried on the Escherichia coli-Streptococcus shuttle vector pDL276, was introduced into S. gordonii DL-1 by natural transformation. One of the transformants (RJMIII) produced a 187-kDa protein (the predicted size of the SpaP-S1 fusion protein) which was recognized by both the anti-pertussis toxin (anti-PT) and anti-SpaP antibodies, suggesting that an in-frame fusion had been made. Results from immunogold-electron microscopic studies and cellular fractionation studies showed that the fusion protein was surface localized and was mainly associated with the cell wall of RJMIII, indicating that SpaP was able to direct the fusion protein to the cell surface. A rabbit antiserum raised against heat-killed S. gordonii RJMIII recognized the native S1 subunit of PT in Western blotting and showed a weak neutralization titer to PT by the Chinese hamster ovary cell-clustering assay. BALB/c mice immunized with the heat-killed S. gordonii RJMIII were protected from the toxic effect of PT in the leukocytosis-promoting and histamine sensitization assays. In conclusion, a fragment of the S1 subunit of PT was successfully surface expressed in S. gordonii; the recombinant S1 fragment was found to be immunogenic and could induce protection against the toxic effect of PT in mice.

Animals↗
PubMed2001

Mosaic genes and mosaic chromosomes: intra- and interspecies genomic variation of Streptococcus pneumoniae.

Streptococcus pneumoniae remains a major causative agent of serious human diseases. The worldwide increase of antibiotic resistant strains revealed the importance of horizontal gene transfer in this pathogen, a scenario that results in the modulation of the species-specific gene pool. We investigated genomic variation in 20 S. pneumoniae isolates representing major antibiotic-resistant clones and 10 different capsular serotypes. Variation was scored as decreased hybridization signals visualized on a high-density oligonucleotide array representing 1,968 genes of the type 4 reference strain KNR.7/87. Up to 10% of the genes appeared altered between individual isolates and the reference strain; variability within clones was below 2.1%. Ten gene clusters covering 160 kb account for half of the variable genes. Most of them are associated with transposases and are assumed to be part of a flexible gene pool within the bacterial population; other variable loci include mosaic genes encoding antibiotic resistance determinants and gene clusters related to bacteriocin production. Genomic comparison between S. pneumoniae and commensal Streptococcus mitis and Streptococcus oralis strains indicates distinct antigenic profiles and suggests a smooth transition between these species, supporting the validity of the microarray system as an epidemiological and diagnostic tool.

Alleles↗
PubMed2001

Conserved DegP protease in gram-positive bacteria is essential for thermal and oxidative tolerance and full virulence in Streptococcus pyogenes.

The DegP protease, a multifunctional chaperone and protease, has been shown to be essential for virulence in gram-negative pathogens such as Salmonella enterica serovar Typhimurium, Brucella abortus, Yersinia enterocolitica, and Pseudomonas aeruginosa. The function of DegP in pathogenesis appears to be the degradation of damaged proteins that accumulate as a result of the initial host response to infection, which includes the release of reactive oxygen intermediates. Additionally, the DegP protease plays a major role in monitoring and maintaining the Escherichia coli periplasm and influences E. coli pilus biogenesis. We report here the identification of highly homologous enzymes in Streptococcus pyogenes, Streptococcus gordonii, Streptococcus mutans, Staphylococcus aureus, and Enterococcus faecalis. Moreover, the phenotype of an insertionally inactivated degP allele in S. pyogenes is similar to that reported for E. coli, with temperature sensitivity for growth and enhanced sensitivity to reactive oxygen intermediates. Virulence studies in a mouse model of streptococcal infection indicate that a functional DegP protease is required for full virulence. These results suggest DegP as an attractive broad-spectrum target for future anti-infective drug development.

Amino Acid Sequence↗
PubMed2003

MtuA, a lipoprotein receptor antigen from Streptococcus uberis, is responsible for acquisition of manganese during growth in milk and is essential for infection of the lactating bovine mammary gland.

A mutant strain of Streptococcus uberis (AJS001) that was unable to grow in bovine milk was isolated following random insertional mutagenesis. The level of growth in milk was restored to that of the parental strain (strain 0140J) following addition of MnSO(4) but not following addition of other metal ions. The mutant contained a single insertion within mtuA, a homologue of mtsA and psaA, which encode metal-binding proteins in Streptococcus pyogenes and Streptococcus pneumoniae, respectively. Strain AJS001 was unable to infect any of eight quarters on four dairy cows following intramammary challenge with 10(5) CFU. Bacteria were never recovered directly from milk of these animals but were detected following enrichment in Todd-Hewitt broth in three of eight milk samples obtained within 24 h of challenge. The animals showed no inflammatory response and no signs of mastitis. Three mammary quarters on two different animals simultaneously challenged with 600 CFU of the parental strain, strain 0140J, became colonized, shed high numbers of S. uberis organisms in milk, displayed a marked inflammatory response to infection, and showed overt signs of mastitis. These data indicate that mtuA was required for efficient uptake of Mn(2+) during growth in bovine milk and infection of the lactating bovine mammary gland.

Animals↗
PubMed2004

Molecular interactions of surface protein peptides of Streptococcus gordonii with human salivary components.

Oral streptococci play a large role in dental biofilm formation, and several types interact as early colonizers with the enamel salivary pellicle to form the primary biofilm, as well as to incorporate other bacteria on tooth surfaces. Interactions of surface molecules of individual streptococci with the salivary pellicle on the tooth surface have an influence on the etiological properties of an oral biofilm. To elucidate the molecular interactions of streptococci with salivary components, binding between surface protein (SspB and PAg) peptides of Streptococcus gordonii and Streptococcus sobrinus were investigated by utilizing BIAcore biosensor technology. The analogous peptide [change of T at position 400 to K in SspB(390-402), resulting in the SspB(390-T400K-402) peptide] from S. gordonii showed the greatest response for binding to salivary components and inhibited the binding of Streptococcus sanguis by more than 50% in a competitive inhibition assay in a comparison with other SspB and PAg peptides. This peptide also bound to the high-molecular-weight protein complex of salivary components and the agglutinin (gp340/DMBT1) peptide (scavenger receptor cysteine-rich domain peptide 2 [SRCRP 2]). In addition, the SspB(390-T400K-402) peptide was visualized by two surface positive charges in connection with the positively charged residues, in which lysine was a key residue for binding. Therefore, the region containing lysine may have binding activity in S. gordonii and S. sanguis, and the SRCRP 2 region may function as a receptor for the binding. These findings may provide useful information regarding the molecular mechanism of early biofilm formation by streptococci on tooth surfaces.

Adhesins, Bacterial↗
PubMed2006

Streptococcus iniae capsule impairs phagocytic clearance and contributes to virulence in fish.

Surface capsular polysaccharides play a critical role in protecting several pathogenic microbes against innate host defenses during infection. Little is known about virulence mechanisms of the fish pathogen Streptococcus iniae, though indirect evidence suggests that capsule could represent an important factor. The putative S. iniae capsule operon contains a homologue of the cpsD gene, which is required for capsule polymerization and export in group B Streptococcus and Streptococcus pneumoniae. To elucidate the role of capsule in the S. iniae infectious process, we deleted cpsD from the genomes of two virulent S. iniae strains by allelic exchange mutagenesis to generate the isogenic capsule-deficient DeltacpsD strains. Compared to wild-type S. iniae, the DeltacpsD mutants had a predicted reduction in buoyancy and cell surface negative charge. Transmission electron microscopy confirmed a decrease in the abundance of extracellular capsular polysaccharide. Gas-liquid chromatography-mass spectrometry analysis of the S. iniae extracellular polysaccharides showed the presence of l-fucose, d-mannose, d-galactose, d-glucose, d-glucuronic acid, N-acetyl-d-galactosamine, and N-acetyl-d-glucosamine, and all except mannose were reduced in concentration in the isogenic mutant. The DeltacpsD mutants were highly attenuated in vivo in a hybrid striped bass infection challenge despite being more adherent and invasive to fish epithelial cells and more resistant to cationic antimicrobial peptides than wild-type S. iniae. Increased susceptibility of the S. iniae DeltacpsD mutants to phagocytic killing in whole fish blood and by a fish macrophage cell line confirmed the role of capsule in virulence and highlighted its antiphagocytic function. In summary, we report a genetically defined study on the role of capsule in S. iniae virulence and provide preliminary analysis of S. iniae capsular polysaccharide sugar components.

Animals↗
PubMed1976

Membrane lipoteichoic acid of Streptococcus pyogenes and its stabilized L-form and the effect of two antibiotics upon its cellular content.

Membrane lipoteichoic acid continues to be synthesized by an osmotically fragile, stabilized L-form of Streptococcus pyogenes. Chromatographic and electrophoretic comparisons indicate that the lipid componenent of lipoteichoic acid in this L-form and its parental streptococcus is glycerophosphoryldiglucosyl diglyceride and not phosphatidylkojibiosyl diglyceride. Based upon dry weight determinations, the yield of lipoteichoic acid from the L-form is 0.19%, as compared with 0.97% from the streptococcus. When grown with bacitracin the L-form contains the same amount of teichoic acid as when grown without this antibiotic; however, its lipoteichoic acid content is reduced by 85%. Similarly, the L-form grown with novobiocin for 10 h contains only 17% of the teichoic acid found in control cells.

Bacitracin↗
PubMed1987

Molecular cloning and characterization of a Streptococcus sanguis DNase necessary for repair of DNA damage induced by UV light and methyl methanesulfonate.

We developed a method for cloning cellular nucleases from streptococci. Recombinant lambda gt11 bacteriophage containing streptococcal nuclease determinants were identified by the production of pink plaques on toluidine blue O DNase plates. We used this technique to clone a 3.2-kilobase-pair EcoRI fragment with DNase activity from the chromosome of Streptococcus sanguis. The locus was designated don (DNase one) and could be subcloned and stably maintained on plasmid vectors in Escherichia coli. Minicell analyses of various subclones of the don locus allowed us to determine the coding region and size of the Don nuclease in E. coli. The don gene product had an apparent molecular mass of 34 kilodaltons and degraded native DNA most efficiently, with lesser activity against denatured DNA and no detectable activity against RNA. S. sanguis don deletion mutants were constructed by transformation of competent cells with in vitro-prepared plasmid constructs. S. sanguis don deletion mutants retained normal transformation frequencies for exogenously added donor DNA. However, when compared with Don+ wild-type cells, these mutants were hypersensitive to DNA damage induced by UV light and methyl methanesulfonate. An S. sanguis don-specific DNA probe detected homology to chromosomal DNA isolated from Streptococcus pneumoniae and Streptococcus mutans Bratthall serogroups d and g. Our results suggested that the don locus was the S. sanguis allele of the previously described S. pneumoniae major exonuclease and was involved in repair of DNA damage. Furthermore, hybridization studies suggested that the don locus was conserved among species of oral streptococci.

Bacterial Proteins↗
PubMed1992

Structural properties and evolutionary relationships of PspA, a surface protein of Streptococcus pneumoniae, as revealed by sequence analysis.

Analysis of the sequence for the gene encoding PspA (pneumococcal surface protein A) of Streptococcus pneumoniae revealed the presence of four distinct domains in the mature protein. The structure of the N-terminal half of PspA was highly consistent with that of an alpha-helical coiled-coil protein. The alpha-helical domain was followed by a proline-rich domain (with two regions in which 18 of 43 and 5 of 11 of the residues are prolines) and a repeat domain consisting of 10 highly conserved 20-amino-acid repeats. A fourth domain consisting of a hydrophobic region too short to serve as a membrane anchor and a poorly charged region followed the repeats and preceded the translation stop codon. The C-terminal region of PspA did not possess features conserved among numerous other surface proteins, suggesting that PspA is attached to the cell by a mechanism unique among known surface proteins of gram-positive bacteria. The repeat domain of PspA was found to have significant homology with C-terminal repeat regions of proteins from Streptococcus mutans, Streptococcus downei, Clostridium difficile, and S. pneumoniae. Comparisons of these regions with respect to functions and homologies suggested that, through evolution, the repeat regions may have lost or gained a mechanism for attachment to the bacterial cell.

Amino Acid Sequence↗