The effect of guanidinium chloride on the behaviour of human cervical-mucus glycoproteins. Evidence for unfolding regions of ordered structure in 6M-guanidinium chloride.
The macromolecular properties of cervical-mucus glycoproteins (mucins) were studied as a function of the concentration of guanidinium chloride with conventional light-scattering, photon-correlation spectroscopy and sedimentation-velocity centrifugation. No evidence for an association of the mucins in 0.2M-NaCl as compared with 6M-guanidinium chloride was found at mucin concentrations below approx. 0.5 mg/ml. However, an increase in the frictional coefficient and in the radius of gyration occurred with increasing concentrations of guanidinium chloride, in particular between 4 M and 6 M, suggesting an expansion of the individual macromolecule. The change in the particle-scattering function is consistent with a transition from a 'stiff' random coil in 0.2 M-NaCl into a more flexible one in 6 M-guanidinium chloride. We suggest that the mucins contain regions of 'ordered' structure which can undergo a reversible 'unfolding' analogous to the behaviour of a conventional globular protein exposed to a denaturing solvent. Such regions might carry sites for specific interactions between mucins and/or be decisive for their conformation and macromolecular properties in physiological solvents.
D002582:Cervix Mucus / Q000032:analysis*; D005260:Female; D019791:Guanidine; D006146:Guanidines; D006801:Humans; D008027:Light; D009077:Mucins; D011487:Protein Conformation; D011489:Protein Denaturation; D012031:Refractometry; D012542:Scattering, Radiation; D012997:Solvents; D014461:Ultracentrifugation
D006146:Guanidines; D009077:Mucins; D012997:Solvents; D019791:Guanidine