Abstract 2302: The mechanism of activation of monomeric B-Raf V600E

Abstract

Abstract B-Raf V600E mutations are frequent in cancer, including over 50% of all melanoma. B-Raf, like many other kinases, undergoes structural changes as it transitions between the inactive and active conformations. Key among these changes are the movement of αC helix from an inactive “OUT” conformation to an active “IN” conformation, and the movement of the activation loop from a closed inactive conformation to an open active conformation. Yet even with the knowledge of what the inactive and active conformations are, questions remain concerning how the V600E mutation activates B-Raf. In particular, we seek to understand why B-Raf V600E is constitutively active in its monomeric state while wild type B-Raf requires dimerization. Here, we investigate the differences between the wild type and mutant B-Raf monomers using molecular dynamics (MD) simulations. We included ATP in the nucleotide binding pocket to more fully explore how it is positioned within B-Raf. Our results show that the 1 µs simulations are too short to capture large conformational changes, however some of the simulations show a transient formation and breaking of the key salt-bridge between Lys483 and Glu501, which gives insight into the movement of the αC helix between the OUT and IN conformations. In addition, the dihedral angles around the DFG motif move towards a more active configuration for B-Raf V600E, while those of the wild type adopt a more inactive orientation. These simulations aid in our understanding of the dynamics of activation in B-Raf V600E. Citation Format: Ryan C. Maloney, Mingzhen Zhang, Hyunbum Jang, Ruth Nussinov. The mechanism of activation of monomeric B-Raf V600E [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2302.