As a serine-threonine protein kinase, glycogen synthase kinase-3 (GSK-3) regulates the synthesis of glycogen and plays important roles in several signaling pathways. it is a key therapeutic target for a number of diseases, such as diabetes, cancer, Alzheimer's disease and chronic inflammation. The conserved Lys85 is important to GSK-3 beta activity and in this paper we illustrate the significant role of Lys85 using dynamic simulation. We find that when Lys85 is Mutated to Arg, one of the two conserved hydrogen bonds between Lys85 and ATP disappears, the salt bridge between Lys85 and Glu97 cannot form, and conformational changes of Phe93. Arg96 and Glu211 occur. These will cause conformational changes of the Substrate binding groove that Would inhibit the activity of GSK-3 beta. MM-GBSA calculations reveal that the K85R Mutation Could lead to a less energy-favorable complex, which is consistent with the structural analysis. 2008 Elsevier Inc. All rights reserved.