Effects of Peutz-Jeghers syndrome (PJS']JS) causing missense mutations L67P, L182P, G242V and R297S on the structural dynamics of LKB1 (Liver kinase B1) protein

The liver kinase B1 (LKB1) is encoded by LKB1 gene. Several pathogenic mutations of LKB1 causing Peutz-Jeghers syndrome and also cancers in breast, gastric, pancreas, and colon have been reported. The present study is focused to analyze the effects on the structural dynamics of LKB1 caused by the 4 pathogenic missense mutations (L67P, L182P, G242V, and R297S), which are reported to reduce the catalytic activity. In this study, the structural changes of LKB1 in apo- and in heterotrimeric complex (LKB1-STRAD alpha-MO25 alpha) form with wild and mutated LKB1 are investigated using all atomistic molecular dynamic simulation. The present study reveals that these four mutations initiate local structural distortions and the solvent accessibility of the surrounding regions of ATP-binding pocket such as glycine-rich loop, alpha B and alpha C loop, activation and catalytic loops. The mutations of L67P, L182P, and G242 V induce distortions of the secondary structure of beta 1-beta 3 sheets, pi - pi interaction (observed between Phe204 of LKB1 and Phe243 of MO25 alpha), and increase the helical properties (both helical twist and length) of the adjacent alpha H-helix, respectively. The active kinase features like the conformation of catalytic and activation loops, salt bridge and, finally, the formation of stable R- and C-hydrophobic spines are also found to be perturbed by these mutations. Hence, the observed mutation-induced structural distortions fail to coordinate the essential binding nature of LKB1 with STRAD alpha and MO25 alpha, which eventually affects the native function of LKB1. These observations are in line with the experimentally reported reduced kinase activity of LKB1.