Calcium Insensitivity and Other Properties of αs1 -I Casein

Abstract

.alpha.s1-I Casein is the large peptide derived from .alpha.s1-casein by splitting off the N-terminal peptide (residues 1-23) by the action of chymosin. .alpha.s1-I casein was in a variety of cheeses and is thought to have a relationship to cheese texture. Properties of .alpha.s1-I and .alpha.s1-caseins were compared. No marked differences were found in conformation between .alpha.s1-I and .alpha.s1-caseins when analyzed by ultracentrifugation and circular dichroism. Ca-binding capacities were similar, but .alpha.s1-I casein lacked the Ca sensitivity characteristic of the .alpha.s1-casein. It is suggested that the hydrophobic N-terminal region of .alpha.s1-casein plays an important role in its precipitation by Ca2+.