Three-dimensional structure of the Hck SH2 domain in solution

The hematopoietic cellular kinase (Hck) is a member of the Src family of non-receptor protein-tyrosine kinases that is expressed predominantly in granulocytes, monocytes and macrophages. Recent observations suggest that Hck may be activated in HIV-infected macrophages and in chronic myelogenous leukemia cells that express Bcr-Abl. In order to increase our understanding of the structural basis for regulation of Hck activity under normal and pathological conditions, we have solved the solution structure of the uncomplexed Hck SH2 domain using NMR spectroscopy. A novel procedure that uses intraresidue H-N-H-alpha distances as references for converting NOE intensities into distance restraints has been described. A total of 1757 significant experimental restraints were derived from NMR spectroscopic data including 238 medium-range and 487 long-range distance restraints and 177 torsion angle restraints. These restraints were used in a simulated annealing procedure to generate 20 structures with the program DYANA. Superimposition of residues 5-104 upon the mean coordinate set yielded an average atomic rmsd values of 0.42+/-0.08 Angstrom for the N,C-alpha,C' atoms and 0.81+/-0.08 Angstrom for all heavy atoms. Rmsd values for those residues in the regions of ordered secondary structure were 0.27+/-0.04 Angstrom for the N,C-alpha,C' atoms and 0.73+/-0.06 Angstrom for all heavy atoms.