AN ASSOCIATING LOW-SULFUR PROTEIN FROM WOOL

The preceding paper described measurements of the molecular weight of the low-sulfur protein component 8 from wool in solutions containing 8 m urea where the molecular weight was found to be 46,000. In this paper a study of the molecular weight of component 8 in 0.01 M sodium borate is reported. It is found that component 8 is an associating system under such conditions and the molecular weight of the smallest unit present is 23,000. The method developed by Adams and Filmer (Adams, E. T., Jr. (1965), Biochemistry 4, 1646; Adams, E. T. Jr., and Filmer, D. L. (1966), Biochemistry 5, 2971) for analyzing sedimentation equilibrium data from a nonideal associating protein system was successful in describing the experimental results in terms of equilibrium constants and a virial coefficient. It is concluded that the system is probably an equilibrium between monomer, dimer, and trimer with the trimer as the polymer in much the greater proportion. © 1968, American Chemical Society. All rights reserved.