ION BINDING BY METMYOGLOBIN

The binding of K+, Na+, Cl-, and SO42- by deionized metmyoglobin from sperm whale skeletal muscle was investigated as a function of pH at 25° with the use of permselective membrane electrodes. Small but definite attachment of K+ and Na+ to myoglobin occurs. A graph of [formula omitted] with respect to [formula omitted] gives a linear relationship for K+; the apparent association constant and number of maximal binding sites for this ion deduced from the plot are 20 and 3.1, respectively. Whereas no binding of Cl- by the native protein can be detected, SO42- ions appear to be held even at the isoionic point. For the latter ion, the plot of [formula omitted] with respect to [formula omitted] does not result in a straight line and the existence of at least two types of sites with different association constants is suggested. © 1968, American Chemical Society. All rights reserved.