THE BINDING OF SURFACE-PROTEINS FROM STAPHYLOCOCCUS-AUREUS TO HUMAN BRONCHIAL MUCINS

Colonization by Staphylococcus aureus is frequently observed in obstru ctive lung diseases, particularly in cystic fibrosis. It has ken shown that the bacteria bind to mucins, the main constituent of bronchial s ecretions, The binding mechanism, however, remains unclear. We have in vestigated the interactions of two strains of S. aureus, one mucoid an d one nonmucoid, with human bronchial mucins, Using a solution phase a ssay, the binding capacity of the two strains to radiolabelled bronchi al mucins was assessed, The bacterial constituents were released by ly sostaphin lysis and the surface components of the nonmucoid strain wer e extracted with the use of a detergent (3-([3-cholamidopropyl] dimeth ylammonio)-1-propane sulphonate (CHAPS)). All were analysed for mucin- binding using an overlay assay. The amount of mucins bound to the nonm ucoid strain was threefold greater than that of the mucoid strain, In the lysostaphin extract from the mucoid strain, only a 57 kDa protein faintly bound I-125-Iabelled mucins, whereas three mucin-binding prote ins (52, 57 and 71 kDa) Here identified from the nonmucoid strain, Two surface proteins, one major at 60 kDa and one minor at 71 kDa, bound radiolabelled bronchial mucins and their binding was almost completely inhibited by ovine submaxillary mucin. These results indicate: 1) dif ferences in the mucin-binding capacity from one strain of S. aureus to another; and 2) the presence of external and internal adhesins bindin g to human respiratory mucins in the nonmucoid strain.