The influence of cations on α-lactalbumin amyloid aggregation.

There is limited knowledge regarding α-lactalbumin amyloid aggregation and its mechanism. We examined the formation of α-lactalbumin amyloid fibrils (α-LAF) in the presence of cations (Mg<sup>2+</sup>, Ca<sup>2+</sup>, Na<sup>+</sup>, K<sup>+</sup>, NH<sub>4</sub><sup>+</sup>, and Cs<sup>+</sup>) in the form of chloride salts at two concentrations. We have shown that studied cations affect the conformation of α-lactalbumin, the kinetics of its amyloid formation, morphology, and secondary structure of α-LAF in a different manner. The higher salts concentration significantly accelerated the aggregation process. Both salt concentrations stabilized α-lactalbumin's secondary structure. However, the presence of divalent cations resulted in shorter fibrils with less β-sheet content. Moreover, strongly hydrated Mg<sup>2+</sup> significantly altered α-lactalbumin's tertiary structure, followed by Na<sup>+</sup>, NH<sub>4</sub><sup>+</sup>, K<sup>+</sup>, and weakly hydrated Cs<sup>+</sup>. On the other hand, Ca<sup>2+</sup>, despite being also strongly hydrated, stabilized the tertiary structure, supposedly due to its high affinity towards α-lactalbumin. Yet, Ca<sup>2+</sup> was not able to inhibit α-lactalbumin amyloid aggregation.