Structure and Stability Analysis of Cytotoxic Complex of Camel α-Lactalbumin and Unsaturated Fatty Acids Produced at High Temperature

alpha-Lactalbumin (alpha-La), together with oleic acid can be converted to a complex, which kills tumor cells selectively. Cytotoxic alpha-La oleic acid and alpha-La linoleic acid complexes were generated by adding fatty acid to camel holo alpha-La at 60 degrees C (referred to as La-OA-60 and La-LA-60 state, respectively). Structural properties of these complexes were studied and compared to the camel alpha-La. The experimental results show that linoleic acid induces alpha-La partial unfolding but oleic acid does not change the protein structure significantly. Also the stability of La-OA-60 and La-LA-60 toward thermal denaturation was measured. The order of temperature at the transition midpoint is as follows: La-LA-60 < La-OA-60 < alpha-La. La-OA-60 complex inhibited tubulin polymerization in vitro. Although the structures of La-OA-60 and La-LA-60 were different, these two complexes had similar cytotoxic effect to DU145 human prostate cancer cells. Samples of La-OA-60 that have been renatured after denaturation lost the specific biological activity toward tumor cells.