FURTHER STUDIES ON ORIGIN AND NATURE OF BOVINE PARA-KAPPA-CASEIN COMPONENTS

1. 1.|In the absence of secondary effects, the insoluble product of rennin (EC 3.4.4.3) action on S-carboxymethyl-κ-casein (SCM-κ-casein) consists of two components, para-SCM-κ-caseins I and II. The C-terminal sequences of the separated species are identical, and this very strongly suggests that the rennin-sensitive bond in the precursor molecule (κ-casein I or II) which gives rise to each is the same. 2. 2.|By treatment with concentrated urea over extended periods of time it is possible to bring about a serial conversion of the para-SCM-κ-casein components to ones carrying a higher net negative charge. This is most probably caused by reaction of the protein species with cyanate derived from urea. Thus, it is not necessary to invoke an attack by rennin at more than one site in each κ-casein molecule to explain observations by other workers of changes in the relative amounts of para-κ-caseins I and II as well as the appearance of a third and more negatively charged species. © 1969.