Calorimetric comparison of the interactions between salivary proteins and Streptococcus mutans with and without antigen I/II.
Antigen I/II can be found on streptococcal cell surfaces and is involved in their interaction with salivary proteins. In this paper, we determine the adsorption enthalpies of salivary proteins to Streptococcus mutans LT11 and S. mutans IB03987 with and without antigen I/II, respectively, using isothermal titration calorimetry. In addition, protein adsorption to the cell surfaces was determined spectrophotometrically. S. mutans LT11 with antigen I/II, yielded a much higher, exothermic adsorption enthalpy at pH 6.8 (ranging from -2073 x 10(-9) to -31707 x 10(-9) microJ per bacterium) when mixed with saliva than did S. mutans IB03987 (-165 x 10(-9) to -1107 x 10(-9) microJ per bacterium) at all bacterial concentrations studied (5 x 10(9), 5 x 10(8), and 5 x 10(7) ml(-1)), largest effects per bacterium being observed for the lowest concentration. However, the enthalpy of salivary protein adsorption to S. mutans LT11 became smaller at pH 5.8. Adsorption isotherms for the S. mutans LT11 showed considerable protein adsorption at pH 6.8 (1.2 - 2.1 mg/m(2)), that decreased only slightly at pH 5.8 (1.1 - 1.6 mg/m(2)), with the largest amount adsorbed at the lowest bacterial concentration. This suggests that the protein(s) in the saliva with the strongest affinity for antigen I/II is (are) readily depleted from saliva. In conclusion, antigen I/II surface proteins on S. mutans play a determinant role in adsorption of salivary proteins through the creation of enthalpically favorable adsorption sites.
Xu
Chun-Ping
CP
Department of Biomedical Engineering, University Medical Center Groningen, University of Groningen, Antonius Deusinglaan 1, 9713 AV Groningen, The Netherlands.
van de Belt-Gritter
Betsy
B
Busscher
Henk J
HJ
van der Mei
Henny C
HC
Norde
Willem
W
D000942:Antigens, Bacterial / Q000737:chemistry / Q000276:immunology* / Q000378:metabolism; D002151:Calorimetry; D006801:Humans; D012471:Salivary Proteins and Peptides / Q000737:chemistry / Q000378:metabolism*; D013295:Streptococcus mutans / Q000737:chemistry / Q000276:immunology* / Q000378:metabolism
D000942:Antigens, Bacterial; D012471:Salivary Proteins and Peptides