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Hydroxylysine-linked glycosides of human complement subcomponent C1q and various collagens.

ABSTRACT: 1. Human C1q, a subcomponent of the first component of complement, contains 67 disaccharides (glucosylgalactose) and 2.4 monosaccharides (galactose) linked to hydroxylysine in one molecule. It was found that 82.6% of the hydroxylsine residues were glycosylated. The suggestion of the possible existence of glucosylgalactosylhydroxylysine reported previously [Yonemasu, Stroud, Niedermeir & Butler (1971) Biochem. Biophys. Res. Commun. 43, 1388--1394] was confirmed. 2. The hydroxylysine-glycosides are not detected in the C-terminal, non-collagen-like, globular regions, but only in the collagen-like regions in the subcomponent C1q molecule. 3. Alpha 1(I) and alpha 2 in pig skin, alpha 1(II) in bovine cartilage and alpha 1(III) in bovine skin collagens contain 2.0, 2.2, 13.2 and 2.0 residues of hydroxylysine-glycosides per molecule, respectively. The percentage of hydroxylysine residues glycosylated in each of these chains is relatively low (on average 38%). 4. Neither the high percentage of hydroxylysine residues glycosylated nor the high values for the ratios of disaccharides to monosaccharides in the subcomponent C1q resembles that in alpha 1(I), alpha 2, alpha 1(II) and alpha 1(III). 5. Similarities between the extent of glycosylation of hydroxylysine residues in collagen-like regions in the subcomponent C1q molecule and that of the collagenous constituents of human glomerular basement membranes, aortic intima, skin A- and B-chains and of bovine anterior lens capsule are discussed.

SUBMITTER: Shinkai H

PROVIDER: S-EPMC1186449 | biostudies-other | 1979 Mar

REPOSITORIES: biostudies-other

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Project description:1. Unreduced human subcomponent C1q was shown by electrophoresis on polyacrylamide gels run in the presence of sodium dodecyl sulphate to be composed of two types of non-covalently linked subunits of apparent mol.wts. 69 000 and 54 000. The ratio of the two subunits was markedly affected by the ionic strength of the applied sample. At a low ionic strength of applied sample, which gave the optimum value for the 54 000-apparent mol.wt. subunit, a ratio of 1.99:1.00 was obtained for the ratio of the 69 000-apparent mol.wt. subunit to the 5400-apparent-mol.wt. subunit. The amount of the 54 000-apparent-mol.wt. subunit detected in the expected position on the gel was found to be inversely proportional to increases in the ionic strength of the applled sample. 2. Human subcomponent C1q on reduction and alkylation, or oxidation, yields equimolar amounts of three chains designated A, B and C [Reid et al. (1972) Biochem. J. 130, 749-763]. The results obtained by Yonemasu & Stroud [(1972) Immunochemistry 9, 545-554], which showed that the 69 000-apparent-mol.wt. subunit was a disulphide-linked dimer of the A and B chains and that the 54 000-apparent-mol.wt. subunit was a disulphide-linked dimer of the C chain, were confirmed. 3. Gel filtration on Sephadex G-200 in 6.0M-guanidinium chloride showed that both types of unreduced subunit were eluted together as a single symmetrical peak of apparent mol.wt. 49 000-50 000 when globular proteins were used as markers. The molecular weights of the oxidized or reduced A, B and C chains have been shown previously to be very similar all being in the range 23 000-24 000 [Reid et al. (1972) Biochem. J. 130, 749-763; Reid (1974) Biochem. J. 141, 189-203]. 4. It is proposed that subcomponent C1q (mol.wt. 410000) is composed of nine non-covalently linked subunits, i.e. six A-B dimers and three C-C dimers. 5. A structure for subcomponent C1q is proposed and is based on the assumption that the collagen-like regions of 78 residues in each of the A, B and C chains are combined to form a triple-helical structure of the same type as is found in collagens.

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Hydroxylysine-linked glycosides of human complement subcomponent C1q and various collagens.

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