Conversion of alpha-lactalbumin to a protein inducing apoptosis

In this study alpha-lactalbumin was converted from the regular, native stat e to a folding variant with altered biological function, The folding varian t was shown to induce apoptosis in tumor cells and immature cells, but heal thy cells were resistant to this effect. Conversion to HAMLET (human alpha- lactalbumin made lethal to tumor cells) required partial unfolding of the p rotein and a specific fatty acid, C18:1, as a necessary cofactor, Conversio n was achieved with alpha-lactalbumin derived from human milk whey and with recombinant protein expressed in Escherichia coil, We thus have identified the folding change and the fatty acid as two key elements that define HAML ET, the apoptosis-inducing functional state of alpha-lactalbumin. Although the environment in the mammary gland favors the native conformation of alph a-lactalbumin that serves as a specifier in the lactose synthase complex, t he conditions under which HAMLET was formed resemble those in the stomach o f the nursing child. Low pH is known to release Ca2+ from the high-affinity Ca2+-binding site and to activate lipases that hydrolyze free fatty acids from milk triglycerides. We propose that this single amino acid polypeptide chain may perform vastly different biological functions depending on its f olding state and the in vivo environment. It may be speculated that molecul es like HAMLET can aid in lowering the incidence of cancer in breast-fed ch ildren by purging of tumor cells from the gut of the neonate.