Some properties of neutral-salt-soluble collagen. 1.

Neutral-salt-soluble collagen is a protein, or group of proteins, involved in collagen anabolism (Harkness, Marko, Muir & Neuberger, 1954; Gross, 1958a; Jackson, 1957) and showing the unusual behaviour of aggregating to typical collagen fibrils when its solutions are warmed to body temperature (Jackson & Fessler, 1955; Gross, Highberger & Schmitt, 1955). One available method of isolation was investigated in the present study and the product characterized. The temperature-dependent ability to form fibres was in part reversible and this led to the fractionation of the material into three parts: fraction A, which formed fibres reversibly; fraction B, which did not form fibres; fraction C, which formed fibres irreversibly. The three fractions were characterized. Coupled with the investigation of the isolation procedure was an estimation of the maximum possible phosphorus content of neutral-salt-soluble collagen, and the apparent rate of incorporation of 32p. This part of the work was prompted by the report of phosphohydroxylysine in calf embryo (Gordon, 1948), together with the occurrence of hydroxylysine in collagen (Van Slyke, Hiller & McFadyen, 1941; Desnuelle & Antonin, 1947), and the presence of neutral-salt-soluble collagen principally in rapidly growing animals (Gross, 1958a). Some of these findings have been briefly reported (Fessler, 1957), and further studies on the temperature-dependent behaviour of neutral-salt-soluble collagens are given in the next paper (Fessler, 1960). Unless specifically stated to the contrary, the term neutral-salt-soluble collagen implies material extracted from the skins of young rabbits and purified by the methods described.