The Neuronal Migration Factor srGAP2 Achieves Specificity in Ligand Binding through a Two-Component Molecular Mechanism

• Published in: Structure (London) 2015-11, Vol.23 (11), p.1989-2000
• Main Authors: Guez-Haddad, Julia, Sporny, Michael, Sasson, Yehezkel, Gevorkyan-Airapetov, Lada, Lahav-Mankovski, Naama, Margulies, David, Radzimanowski, Jens, Opatowsky, Yarden
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Binding Sites; GTPase-Activating Proteins - chemistry; GTPase-Activating Proteins - metabolism; Humans; Ligands; Molecular Docking Simulation; Molecular Sequence Data; Proline-Rich Protein Domains; Protein Binding; src Homology Domains; Substrate Specificity
• ISSN: 0969-2126; 1878-4186
• DOI: 10.1016/j.str.2015.08.009

srGAP proteins regulate cell migration and morphogenesis by shaping the structure and dynamics of the cytoskeleton and membranes. First discovered as intracellular effectors for the Robo1 axon-guidance receptor, srGAPs were later identified as interacting with several other nuclear and cytoplasmic proteins. In all these cases, the srGAP SH3 domain mediates protein-protein interactions by recognizing a short proline-rich segment on the cognate-binding partner. However, as interactions between the isolated SH3 domain and a selected set of ligands show weak affinity and low specificity, it is not clear how srGAPs are precisely recruited to their signaling sites. Here, we report a two-component molecular mechanism that regulates ligand binding to srGAP2 by on the one hand dramatically tightening their association and on the other, moderately autoinhibiting and restricting binding. Our results allow the design of point mutations for better probing of srGAP2 activities, and may facilitate the identification of new srGAP2 ligands. [Display omitted] •The srGAPs' SH3 domain is necessary but not sufficient for effective ligand binding•Effective ligand binding requires the larger F-BAR-RhoGAP-SH3 srGAP module•Ligand binding to srGAP2 is moderately autoinhibited by an SH3 carboxy (C′) extension•The SH3 carboxy (C′) extension utilizes polyproline mimicry and binds in cis or trans srGAP proteins regulate cell migration and morphogenesis by shaping the structure and dynamics of the cytoskeleton and membranes. Guez-Haddad et al. reveal two structural determinants that allow srGAPs to be recruited and placed accurately at their signaling sites.