Structural characterization of the active and inactive states of Src kinase in solution by small-angle X-ray scattering

J Mol Biol. 2008 Feb 15;376(2):492-505. doi: 10.1016/j.jmb.2007.11.066. Epub 2007 Nov 28.


Src kinase plays an important role in several signaling and regulation mechanisms in vivo. Enzymatic activity is tightly regulated through the phosphorylation and dephosphorylation of tyrosine 527, which is placed at the C-terminal tail. Here, we have addressed domain rearrangements involved in the regulation mechanism of Src kinase in solution using small-angle X-ray scattering. In the phosphorylated wild-type form of Src kinase corresponding to the inactive state of the protein, a single conformation compatible with a closed crystallographic structure was found in solution. In the Y527F point mutant representing the active state, analysis of scattering data reveals an equilibrium between two differently populated conformations differing in the radius of gyration by 5 A. The major species (85% of the total population) presents a closed conformation indistinguishable from the crystallographic structure of the inactive state. The minor species (15% of the total population) is an open conformation similar to the crystallographic structure in the active state. The latter structure has the SH3, SH2, and SH2-catalytic domain linker assembled as a pseudo-two-domain protein. The regulation model emerging from this study, including at least three different conformational states, allows the tight regulation of the enzyme without compromising fast response in the presence of natural targets.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Baculoviridae / genetics
  • Catalytic Domain
  • Chelating Agents / pharmacology
  • Chickens
  • Computer Simulation
  • Crystallography, X-Ray
  • DNA, Complementary
  • Edetic Acid / pharmacology
  • Escherichia coli / genetics
  • Models, Molecular
  • Mutation
  • Phosphorylation
  • Protein Conformation
  • Protein Structure, Tertiary
  • Reproducibility of Results
  • Scattering, Small Angle*
  • Solutions / chemistry*
  • Spodoptera / cytology
  • Thermodynamics
  • Transfection
  • X-Ray Diffraction*
  • src-Family Kinases / chemistry*
  • src-Family Kinases / genetics


  • Chelating Agents
  • DNA, Complementary
  • Solutions
  • Edetic Acid
  • src-Family Kinases