alpha-Lactalbumin: structure and function

Small milk protein alpha-lactalbumin (alpha-LA), a component of lactose syn thase, is a simple model Ca2+ binding protein, which does not belong to the EF-hand proteins, and a classical example of molten globule state, It has a strong Ca2+ binding site, which binds Mg2+, Mn2+, Na+, and K+, and severa l distinct Zn2+ binding sites. The binding of cations to the Ca2+ site incr eases protein stability against action of heat and various denaturing agent s, while the binding of Zn2+ to the Ca2+-loaded protein decreases its stabi lity. Functioning of alpha-LA requires its interactions with membranes, pro teins, peptides and low molecular weight substrates and products. It was sh own that these interactions are modulated by the binding of metal cations. Recently it was found that some folding variants of alpha-LA demonstrate ba ctericidal activity and some of them cause apoptosis of tumor cells. (C) 20 00 Federation of European Biochemical Societies.