Effect of the proline analogue azetidine-2-carboxylic acid on collagen synthesis in vivo. II. Morphological and physical properties of collagen containing the analogue.
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abstract
Chick embryos were treated from day 8 to day 12 with 500 g per day of azetidine-2-carboxylic acid. Electron microscopy indicated there were essentially no cross-striated collagen fibrils in tendon or skin of the treated embryos. Amino acid analysis of the tendons suggested that the decrease in cross-striated fibrils was accounted for by the decreased collagen content of the tissue. Acid-soluble collagen isolated from the treated embryos had essentially the same amino acid composition as normal collagen except that it contained about 4 residues of azetidine-2-carboxylic acid per 1000 residues of amino acid. The only demonstrable abnormality in the physical properties of the acid-soluble collagen from treated embryos was that the Tm value for the helix-coil transition was 1.8 lower and the early part of the melting curve was less sharp than the melting curve of the control. The results did not help to resolve the question of whether collagen-containing azetidine-2-carboxylic acid is extruded from cells at a decreased rate because of the presence of the analogue or because of other changes in the molecule. The observations emphasized, however, that incorporation of proline analogues into collagen produces relatively minor changes in the structure of the molecule but that these minor changes have marked effects on the overall rate at which collagen fibrils are deposited in the extracellular matrix. 1971.
