Connective tissue activation. xxxii. structural and biologic characteristics of mesenchymal cell—derived connective tissue activating peptide—v

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Abstract
Connective tissue activating peptide—V (CTAP‐V) is a single‐chain, mesenchymal cell—derived anionic protein with large and small molecular forms (Mr of 28,000 and 16,000, respectively), as defined by sodium dodecyl sulfate—polyacrylamide gel electrophoresis. The proteins have similar specific activities with respect to stimulation of hyaluronic acid and DNA formation in human synovial fibroblast cultures. S‐carboxymethylation or removal of sialic acid residues did not modify CTAP‐V biologic activity. Rabbit antibodies raised separately against each of the purified CTAP‐V proteins reacted, on immunodiffusion and on Western blot, with each antigen and neutralized mitogenic activity. The amino‐terminal amino acid sequence of the CTAP‐V proteins, determined by 2 laboratories, confirmed their structural similarities. The amino‐terminal sequence through 37 residues was demonstrated for the smaller protein. The first 10 residues of CTAP‐V (28 kd) were identical to the N‐terminal decapeptide of CTAP‐V (16 kd). The C‐terminal sequence, determined by carboxy‐peptidase Y digestion, was the same for both CTAP‐V molecular species. The 2 CTAP‐V peptides had similar amino acid compositions, whether residues were expressed as a percent of the total or were normalized to mannose. Reduction of native CTAP‐V protein released sulfhydryl groups in a protein:disulfide ratio of 1:2; this suggests that CTAP‐V contains 2 intramolecular disulfide bonds. Clearly, CTAP‐V is a glycoprotein. The carbohydrate content of CTAP‐V (16 kd) and CTAP‐V (28 kd) is 27% and 25%, respectively. CTAP‐V may have significance in relation to autocrine mechanisms for growth regulation of connective tissue cells and other cell types.