Abstract
Polydisperse proteoglycan subunit from bovine proximal humeral articular cartilage has been separated into a series of relatively monodisperse fractions which have been chemically and physically characterized. The proteoglycan subunit species of the lowest molecular weight contains the least chondroitin sulfate and had an amino acid composition relatively low in serine and glycine and relatively high in cysteine, methionine, and aspartic acid, almost identical to that of the hyaluronic acid-binding region of proteoglycan subunit isolated by Heinegard and Hascall (Heinegard, D., and Hascall, V.C. (1974) J. Biol. Chem. 249, 4250-4256). The molecular weight of proteoglycan subunit increases in proportion to its chondroitin sulfate content. As the molecular weight and chondroitin sulfate content of proteoglycan subunit increase, there is a parallel increase in the serine and glycine contents, and a decrease in the cysteine, methionine, and aspartic acid contents of proteoglycan subunit core protein. The pattern of polydispersity observed strongly supports the concept that proteoglycan subunit core protein contains a hyaluronic acid-binding region of constant size and composition and a polysaccharide attachment region of variable length and composition, composed of repeating peptide sequences containing serine and glycine in equimolar amounts.
Highlights
As the fractions increase in molecular weight, there is an increase in their chondroitin sulfate content and a parallel progressive increase in amino acid residues (Ser, Gly) found predominantly in the polysaccharide attachment region of proteoglycan subunit core
The two sets of data represent the extremes in the values for the yields and analytical data on Fractions Al-D1 through Al-D6 separated from different preparations of Al
We suggest that the 5.7 S to 14.3 S species represent relatively monodisperse fractions of proteoglycan subunit separated on a basis of differences in chemical composition and buoyant density from the polydisperse population of proteoglycan subunits present in Al
Summary
The pattern of polydispersity observed strongly supports the concept that proteoglycan subunit core protein contains a hyaluronic acid-binding region of constant size and composition and a polysaccharide attachment region of variable length and composition, composed of repeating peptide sequences containing serine and glycine in equimolar amounts. In the work reported here, polydisperse proteoglycan subunit from bovine proximal humeral articular cartilage has been separated into a series of relatively monodisperse fractions These fractions have been characterized in terms of chemical composition and sedimentation coefficients. The results reported here support the concept [11] that proteoglycan subunit core protein contains a polysaccharide attachment region of variable length, composed of repeating sequences of peptides containing serine and glycine in equal amounts, which provide the attachment sites for chondroitin sulfate chains. The polydispersity of proteoglycan subunit appears related to the variable length of the polysaccharide attachment region of proteoglycan subunit core protein
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