Calcium-dependent protein interactions in MUC5B provide reversible cross-links in salivary mucus.

摘要: The macromolecular organization within saliva was investigated by tracer diffusion measurements of fluorescent polystyrene microspheres fluorescence recovery after photobleaching using a confocal microscope (confocal-FRAP). There concentration-dependent reduction in microsphere diffusion; this much greater the presence calcium (10 mm) and reduced addition EGTA mm). These effects on showed that native contained sensitive to free concentrations. This supported major increase weight average molecular high mucin fraction (10-62 x 106) an intrinsic viscosity (733 1203 ml/g) both caused calcium. Analysis change 20-fold apparent pore size (from 130 nm 10 mm CaCl2 2600 at physiological concentration). effect specific for unaffected up 2 m NaCl. binding activity buoyant density excluded from Sepharose CL-2B. Calcium gave approximate Kd 7 10-6 m, irreversibly destroyed treatment with 6 guanidinium chloride mild reduction, suggesting it be protein site. shown contain MUC5B as single species positive ion electrospray ionization-tandem mass spectrometry analysis. results suggested oligomeric is assembled into larger linear or branched assemblies through calcium-mediated cross-links.