FRATide

Mechanism of kinase inactivation and nonbinding of FRATide to GSK3beta due to K85M mutation: molecular dynamics simulation and normal mode analysis.[Pubmed:21442609]

Biopolymers. 2011 Oct;95(10):669-81.

As a serine/threonine protein kinase, glycogen synthase kinase 3beta (GSK3beta) is an essential component of several cellular processes, including insulin, growth factor, and Wnt signaling. The conserved K85 is important to GSK3beta activity and FRATide binding. To elucidate the mechanisms concerning kinase inactivation and nonbinding of FRATide to GSK3beta, molecular dynamics (MD) simulation, molecular mechanics generalized Born/surface area (MM_GBSA) calculation, and normal mode analysis (NMA) were performed on both the wild-type (WT) and the K85M mutation of the GSK3beta-FRATide complex. The results revealed that the periodic open-closed conformational change of the G loop, together with the compact conformation of the RD pocket, was disturbed in the K85M mutant, in contrast to those in the WT. This in turn caused inhibition of GSK3beta. Specifically, the correct folding pattern of GSK3beta was disrupted in the K85M mutant, resulting in the loss of two key hydrogen bonds between K214 of FRATide and E290 and K292 of GSK3beta, respectively. Furthermore, MM_GBSA calculations indicated that the K85M mutation could lead to a less energy-favorable GSK3beta-FRATide complex. In addition, NMA demonstrated that the "rocking" of the N- and C-terminal domains of GSK3beta, which coordinates the mutual movement of both lobes, inducing the opening and closing of the active site of GSK3beta, which may assist the entry of ATP into the ATP binding site and the release of the ADP product. Strikingly, this phenomenon was not clearly observed in the K85M mutation. This study provides a structural basis for the effect of the K85M mutation on the GSK3beta-FRATide complex.

Effect of double mutations K214/A-E215/Q of FRATide on GSK3beta: insights from molecular dynamics simulation and normal mode analysis.[Pubmed:21912861]

Amino Acids. 2012 Jul;43(1):267-77.

Glycogen synthase kinase 3beta (GSK3beta) is a multifunctional serine/threonine protein kinase that is involved in several biological processes including insulin and Wnt signaling pathways. The Wnt signaling via FRAT-mediated displacement of axin inhibits GSK3beta activity toward non-primed substrates without affecting its activity toward primed substrates. Herein, molecular dynamics simulation, molecular mechanics generalized Born/surface area (MM_GBSA) calculation, and normal mode analysis are performed to explore the structural influence of the double mutations K214/A-E215/Q of FRATide on the GSK3beta-FRATide complex. The results reveal that the priming phosphate-binding site, the primed substrate-binding site, the alignment of the critical active site residues in the ATP-binding site, as well as the periodic open-closed conformational change of the ATP-binding site, which are critical for the catalytic activity of GSK3beta, are negligibly influenced in the mutated system compared with the wild-type (WT) system. This indicates that FRATide does not inhibit the GSK3beta activity toward primed substrates. Additionally, MM_GBSA calculation indicates that the less energy-favorable GSK3beta-FRATide complex is observed in the mutant than in the WT complex.