Two-state dynamics of the SH3-SH2 tandem of Abl kinase and the allosteric role of the N-cap. Proc Natl Acad Sci U S A 2013 Sep 03;110(36):E3372-80
Date
08/21/2013Pubmed ID
23959873Pubmed Central ID
PMC3767523DOI
10.1073/pnas.1303966110Scopus ID
2-s2.0-84883405702 (requires institutional sign-in at Scopus site) 36 CitationsAbstract
The regulation and localization of signaling enzymes is often mediated by accessory modular domains, which frequently function in tandems. The ability of these tandems to adopt multiple conformations is as important for proper regulation as the individual domain specificity. A paradigmatic example is Abl, a ubiquitous tyrosine kinase of significant pharmacological interest. SH3 and SH2 domains inhibit Abl by assembling onto the catalytic domain, allosterically clamping it in an inactive state. We investigate the dynamics of this SH3-SH2 tandem, using microsecond all-atom simulations and differential scanning calorimetry. Our results indicate that the Abl tandem is a two-state switch, alternating between the conformation observed in the structure of the autoinhibited enzyme and another configuration that is consistent with existing scattering data for an activated form. Intriguingly, we find that the latter is the most probable when the tandem is disengaged from the catalytic domain. Nevertheless, an amino acid stretch preceding the SH3 domain, the so-called N-cap, reshapes the free-energy landscape of the tandem and favors the interaction of this domain with the SH2-kinase linker, an intermediate step necessary for assembly of the autoinhibited complex. This allosteric effect arises from interactions between N-cap and the SH2 domain and SH3-SH2 connector, which involve a phosphorylation site. We also show that the SH3-SH2 connector plays a determinant role in the assembly equilibrium of Abl, because mutations thereof hinder the engagement of the SH2-kinase linker. These results provide a thermodynamic rationale for the involvement of N-cap and SH3-SH2 connector in Abl regulation and expand our understanding of the principles of modular domain organization.
Author List
Corbi-Verge C, Marinelli F, Zafra-Ruano A, Ruiz-Sanz J, Luque I, Faraldo-Gómez JDAuthor
Fabrizio Marinelli PhD Associate Professor in the Biophysics department at Medical College of WisconsinMESH terms used to index this publication - Major topics in bold
AlgorithmsAllosteric Regulation
Calorimetry, Differential Scanning
Catalytic Domain
Crystallography, X-Ray
Humans
Models, Molecular
Molecular Dynamics Simulation
Mutation
Protein Conformation
Protein Structure, Tertiary
Proto-Oncogene Proteins c-abl
Thermodynamics
src Homology Domains
