1blk
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NMR ENSEMBLE OF BLK SH2 DOMAIN USING CHEMICAL SHIFT REFINEMENT, 20 STRUCTURES
OverviewOverview
Signal transduction in B cells is mediated, in part, by the interaction of, the cytoplasmic components of the antigen receptor complex and various, members of the src family tyrosine kinases. Key to this process appears to, be the interaction of the tyrosine kinase SH2 domains with the, tyrosine-phosphorylated cytoplasmic domain of Ig-alpha, a disulfide-bonded, heterodimeric (with Ig-beta or Ig-gamma) transmembrane protein that, noncovalently associates with the antigen receptor immunoglobin chains. In, addition to binding to the phosphorylated cytoplasmic domains of Ig-alpha, and Ig-beta, blk and fyn(T), two members of the src family kinases, have, been shown to bind overlapping but distinct sets of phosphoproteins [Malek, & Desiderio (1993) J. Biol. Chem. 268. 22557-22565]. A comparison of their, three-dimensional structures may elucidate the apparently subtle, differences required for phosphoprotein discrimination. To begin, characterizing the blk/fyn/phosphosphoprotein interactions, we have, determined the three-dimensional solution structure of the SH2 domain of, blk kinase by nuclear magnetic resonance (NMR) spectroscopy. 1H, 13C, and, 15N resonances of the SH2 domain of blk kinase were assigned by analysis, of multidimensional, double- and triple-resonance NMR experiments. Twenty, structures of the blk SH2 domain were refined with the program X-PLOR, using a total of 2080 experimentally derived conformational restraints., The structures converged to a root-mean-squared (rms) distance deviation, of 0.51 and 0.95 A for the backbone atoms and for the non-hydrogen atoms, respectively. The blk SH2 domain adopts the prototypical SH2 fold., Structurally, blk SH2 is most similar to the crystal structure of the, v-src SH2 domain [Waksman et al. (1993) Nature 358.646-653] and, superimposes on the crystal structure with an rmsd of 1.52 A for the, backbone atoms. The largest deviations occur in the four loops, interconnecting beta-strands A-E, which are the least well-defined regions, in the NMR structure. Exclusion of these loops lowers this rmsd to 0.82 A., The conformation of the BC loop in the blk SH2 domain is similar to the, open conformation in the apo lck SH2 domain, suggesting that, like the lck, SH2 domain, the blk SH2 domain may have a gated phosphopeptide binding, site. Finally, it is proposed that the amino acid substitution of Lys 88, (blk) for Glu [fyn(T)] is important for the observed differences in, specificity between blk and fyn(T) SH2 domains.
About this StructureAbout this Structure
1BLK is a Single protein structure of sequence from Mus musculus. Active as Transferase, with EC number and 2.7.10.2 2.7.10.1 and 2.7.10.2 Full crystallographic information is available from OCA.
ReferenceReference
The three-dimensional solution structure of the SH2 domain from p55blk kinase., Metzler WJ, Leiting B, Pryor K, Mueller L, Farmer BT 2nd, Biochemistry. 1996 May 21;35(20):6201-11. PMID:8639560
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