Probing the Ras‐membrane Interaction from a Structural Biology Perspective

Abstract

The small GTPase Ras is involved in a multitude of cellular signaling pathways that culminate in changes in transcription levels to control cell differentiation, growth, and apoptosis. The three major isoforms, H-, K-, and N-Ras signal from membrane “hubs” when bound to GTP, while signaling is turned off by nucleotide hydrolysis to GDP. Though the isoforms share greater than 90 percent sequence identity and a conserved global structure, each can promote overlapping yet distinct signaling outputs. Sublocalization within different microdomains and the orientation of each protein with respect to the membrane have been implicated in promoting these isoform-specific characteristics. To date, structural biology studies have focused on the effector lobe of the protein, which harbors mutations in around 20% of human cancers, while other biophysical approaches have been used to discern the details of the C-terminal hypervariable (HVR) region and its role in membrane association and localization. The research presented here focuses on the atomic level interactions between Ras and the membrane from a structural biology perspective. Crystal structures of H-Ras in the presence of membrane phospholipid head group mimics will be presented, with the goal of identifying the types and specificity of interactions at the Ras-membrane interface.