Effect of nonenzymatic deamidation on the structure stability of Camelus dromedarius α-lactalbumin

摘要

Camelid alpha-lactalbumin is the only known protein that can undergo nonenzymatic deamidation on two Asn residues. This leads to the generation of a mixture of unusual isoAsp and D-Asp residues that may impact health. The effect of deamidation on camel alpha-lactalbumin instability was investigated. Circular dichroism showed that the altered protein acquired secondary structure resulting in an increase in alpha-helix content. In good agreement, the 3D structure of camel alpha-lactalbumin determined by X-ray crystallography, displayed a short additional alpha-helix probably induced by deamidation, compared to the human and bovine counterparts. This alpha-helix was located in the C-terminal region and included residues 101-106. Differential scanning calorimetry together with the susceptibility to thermolysin showed that the deamidation process reinforced the structural stability of the alpha-lactalbumin at high temperature and its resistance toward proteolysis.