The structures of the MAP kinase p38 in complex with docking site peptides containing a phi(A)-X-phi(B) motif, derived from substrate MEF2A and activating enzyme MKK3b, have been solved. The peptides bind to the same site in the C-terminal domain of the kinase, which is both outside the active site and distinct from the "CD" domain previously implicated in docking site interactions. Mutational analysis on the interaction of p38 with the docking sites supports the crystallographic models and has uncovered two novel residues on the docking groove that are critical for binding. The two peptides induce similar large conformational changes local to the peptide binding groove. The peptides also induce unexpected and different conformational changes in the active site, as well as structural disorder in the phosphorylation lip.

WNK1 [with no lysine (K)] is a serine-threonine kinase associated with a form of familial hypertension. WNK1 is at the top of a kinase cascade leading to phosphorylation of several cotransporters, in particular those transporting sodium, potassium, and chloride (NKCC), sodium and chloride (NCC), and potassium and chloride (KCC). The responsiveness of NKCC, NCC, and KCC to changes in extracellular chloride parallels their phosphorylation state, provoking the proposal that these transporters are controlled by a chloride-sensitive protein kinase. Here, we found that chloride stabilizes the inactive conformation of WNK1, preventing kinase autophosphorylation and activation. Crystallographic studies of inactive WNK1 in the presence of chloride revealed that chloride binds directly to the catalytic site, providing a basis for the unique position of the catalytic lysine. Mutagenesis of the chloride binding site rendered the kinase less sensitive to inhibition of autophosphorylation by chloride, validating the binding site. Thus, these data suggest that WNK1 functions as a chloride sensor through direct binding of a regulatory chloride ion to the active site, which inhibits autophosphorylation.

Among eukaryotic protein kinases, 1 the Ser/Thr kinases have been classified into six large groups. These are named the AGC group, the CaMK group (for calcium-calmodulin dependent), the CMGC group (for CDK, MAP kinase, glycogen synthase kinase, and CDKlike), the STE group (homologs of STE11 and STE20), and the CK1 group (for casein kinase-1), and TKL (tyrosine kinase like). Structural data is now available for representatives of each of the well-populated groups, as well as smaller groups, such as WNKs (with no lysine), 18 revealing that the protein kinases have a common architecture. 2.1. Architecture of Protein Kinases Protein kinases possess a two-lobe architecture that has been reviewed several times (Figure 1a). 6,7,19,2021 Briefly, the N-terminal lobe is composed of a five-stranded β-sheet and a single well-conserved helix, labeled helix C based on the structure of PKA. 19 The Cterminal lobe possesses 6 large helices (D, E, F, G, H, and I) and two β-ribbons, β7-β8 and β6-β9. The β7-β8 ribbon is present in both active and inactive protein kinases. Further, an additional β-strand interacts with β7-β8 forming a 3-stranded β-sheet in most protein kinases, but not in PKA. The β-strand is labeled β5D for its placement in the structure between β-strand 5 and helix D (Figure 1a). The β6-β9 ribbon is present only in active kinases (Figure 1a); 21 β9 is part of the activation segment. Two smaller helices, labeled P+1 and APE (also called helix αEF) 21 in Figure 1a, are conserved in active protein kinases. The activation segment and the catalytic loop are also in the C-terminal lobe. The catalytic loop refers to a 7-residue segment (Asp166-Asn172 in PKA) that houses the catalytic aspartate (Asp 166) and lysine residue (Lys168). The activation segment refers to the sequence flanked by the conserved motifs DFG (following β8; subdomain VII in the nomenclature of Hanks and Hunter 22) and APE (subdomain VIII) (also referred to as "activation loop" or Lip). This segment is variable in size and in many kinases possesses one or more phosphorylation sites that tend to be activating. 21 The primary substrate recognition pocket, the P+1 binding site, is adjacent to, and contiguous in sequence with, the activation segment (Figure 1b). Further, relatively short (~50 residue) N-and C-terminal extensions from the kinase core may pack on the core, and are present for all of the Ser/Thr kinases studied crystallographically, including the smallest, CDK2. 23 Longer N-and C-terminal extensions are known to fold into a variety of separate domains (as reviewed in ref 1). Structural data for Ser/Thr kinases possessing separately folded domains (either a separate subunit or folding unit) is available for twitchin 24 , p21-activated protein kinase (PAK1), 25 CK2 (casein kinase-2), 26 G-protein-coupled receptor kinase-2 (GRK2), 27 and PKA. 28 Protein kinases have grooves on the surface of the kinase core (Figure 1b). The grooves are a consequence of the architecture, and tend to be conserved. For example, in the structure of PKA, a groove is p...

Map kinases are drug targets for autoimmune disease, cancer, and apoptosis-related diseases. Drug discovery efforts have developed MAP kinase inhibitors directed toward the ATP binding site and neighboring "DFG-out" site, both of which are targets for inhibitors of other protein kinases. On the other hand, MAP kinases have unique substrate and small molecule binding sites that could serve as inhibition sites. The substrate and processing enzyme D-motif binding site is present in all MAP kinases, and has many features of a good small molecule binding site. Further, the MAP kinase p38alpha has a binding site near its C-terminus discovered in crystallographic studies. Finally, the MAP kinases ERK2 and p38alpha have a second substrate binding site, the FXFP binding site that is exposed in active ERK2 and the D-motif peptide induced conformation of MAP kinases. Crystallographic evidence of these latter two binding sites is presented.

Traditionally, ligands used in asymmetric catalysis have contained either stereogenic atoms or hindered single bonds (atropisomerism), or both. Here we demonstrate that allenes, chiral 1,2-dienes, appended with basic functionality can serve as ligands for transition metals. We describe an allene-containing bisphosphine that, when coordinated to Rh(I), promotes the asymmetric addition of aryl boronic acids to α-keto esters with high enantioselectivity. Solution and solid-state structural analysis reveals that one olefin of the allene can coordinate to transition metals generating bi- and tri-dentate ligands.