Electrostatic interactions in the binding pathway of a transient protein complex studied by NMR and isothermal titration calorimetry.
Related Articles Electrostatic interactions in the binding pathway of a transient protein complex studied by NMR and isothermal titration calorimetry.
J Biol Chem. 2014 Aug 13;
Authors: Meneses E, Mittermaier A
Abstract
Much of our knowledge of protein binding pathways is derived from extremely stable complexes that interact very tightly, with lifetimes of hours to days. Much less is known about weaker interactions and transient complexes, since these are challenging to characterize experimentally. Nevertheless, these types of interactions are ubiquitous in living systems. The combination of NMR relaxation dispersion CPMG experiments and isothermal titration calorimetry allows the quantification of rapid binding kinetics for complexes with sub-millisecond lifetimes that are difficult to study using conventional techniques. We have used this approach to investigate the binding pathway of the Src Homology 3 (SH3) domain from the Fyn tyrosine kinase, which forms complexes with peptide targets whose lifetimes are on the order of about a millisecond. Long-range electrostatic interactions have been shown to play a critical role in the binding pathways of tightly-binding complexes. The role of electrostatics in the binding pathways of transient complexes is less well understood. Similarly to previously-studied tight complexes, we find that SH3 domain association rates are enhanced by long-range electrostatics, while short-range interactions are formed late in the docking process. However, the extent of electrostatic association rate enhancement is several orders of magnitudes less, while the electrostatic-free basal association rate is significantly greater. Thus the SH3 domain is far less reliant on electrostatic enhancement to achieve rapid association kinetics than are previously studied systems. This suggests there may be overall differences in the role played by electrostatics in the binding pathways of extremely stable versus transient complexes.
PMID: 25122758 [PubMed - as supplied by publisher]
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