The isolation of a soluble type III collagen precursor from rat skin

A soluble form of type III collagen has been isolated from the 1.0 M NaCl neutral salt soluble extract of rat skin. This component has a molecular weight of 350,000 and is converted by reduction and alkylation to three identical α-chains with molecular weight 118,000. Segment-long-spacing precipitates produced from the renatured disulfide-linked component are about 300 Å longer than collagen with extensions at both the amino and carboxyl terminal ends. Pepsin treatment removes both amino and carboxyl terminal extensions. These and radioisotope incorporation data lead to the conclusion that this component is a precursor of the αl(III)₃] collagen.