Collagen production by the free‐living nematode Panagrellus silusiae in the presence of the proline analogue L‐azetidine‐2‐carboxylic acid

Abstract

AbstractThe effect of the proline analogue, L‐azetidine‐2‐carboxylic acid, on growth and collagen synthesis in the free‐living nematode Panagrellus silusiae was examined. Morph metrically, the worms showed no evidence of an adverse response to the long term presence of azetidine carboxylic acid (20 mM/ml) in the growth media. Incorporation of labelled proline into protein was specifically blocked by the analogue; whereas the uptake of radiolabel led leucine into polypeptides was unaffected. Conversely, the uptake of labelled azetidine carboxylate was antagonized only by proline. The incorporation of labelled analogue into collagen during postembryonic development paralleled the discontinuous pattern of collagen biosynthesis in untreated worms. Cuticular collagens became labelled after incubation with [14C]‐azetidine carboxylate. These results suggest that the analogue is incorporated into collagenous and noncollagenous proteins. To substantiate this point, amino acid analyses of cuticles that were isolated from azetidine carboxylate‐treated worms revealed that the analogue can replace at least 39% of the imino acid residues of the cuticular collagens. Thus, resistance to azetidine carboxylic acid in this organism is not due totally to the metabolic breakdown of the analogue. Although the extent to which noncollagenous proteins incorporate the analogue was not determined directly, it is likely that azetidine carboxylic acid is incorporated into diverse globular proteins without a complete loss of activity of the substituted molecules. Certainly, in the cuticular collagens the analogue can readily replace prolyl residues without any apparent deleterious consequences.