The macromolecular structure of human cervical-mucus glycoproteins. Studies on fragments obtained after reduction of disulphide bridges and after subsequent trypsin digestion

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Abstract
Human cervical-mucus glycoproteins (mucins) were extracted with 6 M guanidinium chloride in the presence of proteinase inhibitors and purified by isopycnic density-gradient centrifugations. The whole mucins (MW approximately 10 .times. 106) were degraded into subunits (MW approximately 2 .times. 106) by reduction of disulfide bonds. Trypsin digestion of the subunits produced glycopeptides with MW approximately 380,000, which appear to be rod-like with a length of approximately 105 nm. The relationship between the radius of gyration and the MW value obtained by light-scattering for whole mucins, subunits and domains suggest that cervical-mucus glycoproteins are linear flexible macromolecules composed of, on the average, 4 or 5 domains/subunit and 4 subunits/whole mucin macromolecule. The shape-dependent particle scattering function for the whole mucins and the subunits are in accordance with that of a linear flexible chain. No evidence for a branched or a star-like structure was found. A tentative model for cervical mucins is proposed.