3pdt
Crystal Structure of the C-terminal Truncated Alpha-Kinase Domain of Myosin Heavy chain Kinase
Structural highlights
FunctionMHCKA_DICDI Phosphorylates threonine in the C-terminal tail region of myosin II heavy chain. This phosphorylation is critical in regulating the assembly and disassembly of myosin II filament. Requires autophosphorylation for activity. Publication Abstract from PubMedDictyostelium discoideum myosin II heavy chain kinase A (MHCK A), a member of the atypical alpha-kinase family, phosphorylates sites in the myosin II tail that block filament assembly. Here we show that the catalytic activity of A-CAT, the alpha-kinase domain of MHCK A (residues 552-841), is severely inhibited by the removal of a disordered C-terminal tail sequence (C-tail; residues 806-841). The key residue in the C-tail was identified as Thr825, which was found to be constitutively autophosphorylated. Dephosphorylation of Thr825 using shrimp alkaline phosphatase decreased A-CAT activity. The activity of a truncated ACAT lacking Thr825 could be rescued by Pi, phosphothreonine and a phosphorylated peptide, but not by threonine, glutamic acid, aspartic acid or an unphosphorylated peptide. These results focused attention on a Pi-binding pocket located in the C-terminal lobe of A-CAT. Mutational analysis demonstrated that the Pi-pocket was essential for A-CAT activity. Based on these results, it is proposed that autophosphorylation of Thr825 activates ACAT by providing a covalently-tethered ligand for the Pi-pocket. Ab initio modeling studies using the Rosetta FloppyTail and FlexPepDock protocols showed that it is feasible for the phosphorylated Thr825 to dock intramolecularly into the Pi-pocket. Allosteric activation is predicted to involve a conformational change in Arg734, which bridges the bound Pi to Asp762 in a key active site loop. Sequence alignments indicate that a comparable regulatory mechanism is likely to be conserved in Dictyostelium MHCK B-D and metazoan eukaryotic elongation factor-2 kinases. Autophosphorylation activates Dictyostelium myosin II heavy chain kinase A by providing a ligand for an allosteric binding site in the {alpha}-kinase domain.,Crawley SW, Samimi Gharaei M, Ye Q, Yang Y, Raveh B, London N, Schueler-Furman O, Jia Z, Cote GP J Biol Chem. 2010 Nov 11. PMID:21071445[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
| ||||||||||||||||||||
