The effect of a Pro²⁸Thr point mutation on the local structure and stability of human galactokinase enzyme-a theoretical study.

Galactokinase is responsible for the phosphorylation of α-D: -galactose, which is an important step in the metabolism of the latter. Malfunctioning of galactokinase due to a single point mutation causes cataracts and, in serious cases, blindness. This paper reports a study of the Pro(28)Thr point mutation using a variety of theories including molecular dynamics (MD), MM-PBSA/GBSA calculations and AIM analysis. Altered H-bonding networks were detected based on geometric and electron density criteria that resulted in local unfolding of the β-sheet secondary structure. Another consequence was the decrease in stability (5-7 kcal mol(-1)) around this region, as confirmed by ΔG(bind) calculations for the extracted part of the whole system. Local unfolding was verified by several other MD simulations performed with different duration, initial velocities and force field. Based on the results, we propose a possible mechanism for the unfolding caused by the Pro(28)Thr point mutation.