title: Role of lysine in interaction between surface protein peptides of Streptococcus gordonii and agglutinin peptide.
abstract: BACKGROUND
  Streptococcus gordonii interacts with the salivary pellicle on the tooth surface and plays an important role in dental biofilm formation. Reports show that the analog Ssp peptide (A11K; alanine to lysine at position 11 in the arranged sequence, (1)DYQAKLAAYQAEL(13)) of SspA and SspB of S. gordonii increased binding to the salivary agglutinin (gp-340/DMBT1) peptide (scavenger receptor cysteine-rich domain 2: SRCRP2). To determine the role of lysine in the binding of the Ssp(A11K) peptide to SRCRP2, we investigated whether an additional substitution by lysine influenced the binding of Ssp(A11K) peptide to SRCRP2 using a BIAcore biosensor assay.
  
  
  METHODS
  Six analogs of the Ssp peptide with positive charges in surface positions on the structure were synthesized using substitution at various positions.
  
  
  RESULTS
  The binding activity of analog Ssp(A4K-A11K) peptide was significantly higher than the other Ssp analogs. The binding activity rose under low ionic strength conditions. The distance between positively charged amino acids in the Ssp(A4K-A11K) peptide between 4K and 11K was 1.24 +/- 0.02 nm and was close to the distance (1.19 +/- 0.00 nm) between Q and E, presenting a negative charged area, on SRCRP2 using chemical computing graphic analysis. The molecular angle connecting 1D-11K-4K in the Ssp(A4K-A11K) peptide secondary structure was smaller than the other peptide angles (1D-11K-XK). The Ssp(A4K-A11K) peptide showed higher inhibiting activity for Streptococcus mutans binding to saliva-coated hydroxyapatite than the (A11K) peptide.
  
  
  CONCLUSIONS
  The positioning of lysine is important for binding between Ssp peptide and SRCRP2, and the inhibiting effect on S. mutans binding to the tooth surface.
authors.affiliation: Department of Cariology and Operative Dentistry, Tokyo Medical and Dental University, Tokyo, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Koba
authors.forename: K
authors.initials: K
authors.lastname: Okuda
authors.forename: H
authors.initials: H
authors.lastname: Watanabe
authors.forename: J
authors.initials: J
authors.lastname: Tagami
authors.forename: H
authors.initials: H
authors.lastname: Senpuku
mesh_terms: D018829:Adhesins, Bacterial / Q000235:genetics / Q000378:metabolism*; D000328:Adult; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D023181:Antimicrobial Cationic Peptides / Q000378:metabolism; D001667:Binding, Competitive; D002135:Calcium-Binding Proteins; D004268:DNA-Binding Proteins; D044622:Dental Pellicle / Q000378:metabolism*; D017886:Durapatite / Q000378:metabolism; D006801:Humans; D008239:Lysine / Q000235:genetics / Q000502:physiology*; D008969:Molecular Sequence Data; D009842:Oligopeptides; D011485:Protein Binding; D017433:Protein Structure, Secondary; D011956:Receptors, Cell Surface / Q000235:genetics / Q000378:metabolism*; D051128:Scavenger Receptors, Class F / Q000235:genetics / Q000378:metabolism; D054773:Streptococcus gordonii / Q000235:genetics / Q000378:metabolism*; D013295:Streptococcus mutans / Q000378:metabolism; D013499:Surface Properties; D025521:Tumor Suppressor Proteins
chemical_list: D018829:Adhesins, Bacterial; D023181:Antimicrobial Cationic Peptides; D002135:Calcium-Binding Proteins; C108174:DMBT1 protein, human; D004268:DNA-Binding Proteins; D009842:Oligopeptides; D011956:Receptors, Cell Surface; D051128:Scavenger Receptors, Class F; C000622268:Ssp(A4K-A11K) peptide; C082314:SspA protein, bacteria; D025521:Tumor Suppressor Proteins; C068465:salivary agglutinin receptor, Streptocococcus; D017886:Durapatite; D008239:Lysine