Interactions of rat alpha-foetoprotein with bilirubin.

The binding of bilirubin to rat-alpha-foetoprotein has been measured by changes in the absorption spectrum and by the appearance of two intense circular-dichroism bands. Furthermore binding of this bile pigment has been demonstrated by a decrease of its enzymic oxidation rate and by competition experiments with bovine serum albumin-agarose. The binding parameters have been determined as follows: n = 1.0 mol bound/mol of protein and Ka = 2.9 X 10(6) M-1. Competition of oestradiol for the bilirubin-binding site has not been established.