Solution structure of GAP SH3 domain by 1H NMR and spatial arrangement of essential Ras signaling-involved sequence

Abstract

Src homology 3 (SH3) domains are found in numerous cytoplasmic proteins involved in intracellular signal transduction We used 2-D 1H NMR to determine the structure of the SH3 domain of the guanosine triphosphatase-activating protein (GAP), an essential component of the Ras signaling pathway. The structure of the GAP SH3 domain (275-350) was found to be a compact β-barrel made of six antiparallel β-strands arranged in two roughly perpendicular β-sheets with the acidic residues located at the surface of the protein. The Trp317, Trp319, Thr321 and Leu323 residues belonging to the sequence (317-326), which was shown to be essential for Ras signaling, formed two nearby lipophilic bulges followed by a hydrophilic domain (Arg324-Asp326) These structural data could be used to characterize the still unidentified downstream components of GAP, which are involved in Ras signaling, and to rationally design inhibitors of this pathway.