Protein Kinase A (PKA)Huse and Kuriyan, 2002The PKA structure has twomain lobes (subdomains).Huse and Kuriyan, 2002Schematized PKA structureHuse and Kuriyan, 2002The phosphate binding loop contains aconserved glycine-rich sequence motif.Phosphatebinding loop(P loop)Huse and Kuriyan, 2002The P-loop contains severalcompletely conserved glycinesαβγThe three phosphates of adenosine tri-phosphate are labeledα, β, and γA protein kinase might be expectedto phosphorylate which substratebest?A. Free serine, threonine or tyrosineamino acids.B. Native structure protein substrate.C. Denatured protein substrate.D. A peptide containing aphosphorylatable residue.The peptide substrate binds in anextended conformation across the front ofthe PKA structure.PeptidesubstrateHuse and Kuriyan, 2002Substrate (in yellow) binds acrossthe front of the structure.Huse and Kuriyan, 2002Each protein kinase haspreferred substrates.Kinase surface features help to determineits preferred substrates.Ubersax and Ferrell, 2007The activation loop provides a platformupon which the substrate sits.Huse and Kuriyan, 2002Activation loop (green)The activation loop (in orange) is stabilized inan extended conformation when it isphosphorylated.Huse and Kuriyan, 2002Lys72 makes contacts withthe α and β phosphate groupsHuse and Kuriyan, 2002Glu91, a residue in the αC helix, stabilizes andorients Lys72.Huse and Kuriyan, 2002Lys72αC, with Glu91extending from itPositions of K72 and E91 inother kinasesProtein kinases:A. Are always close to 300 a.a. in length.B. Phosphorylate all available S, T, or Yresidues in their protein substrate.C. All have very similar conformationswhen active, but dissimilarconformations when inactive.D. Can use ATP or GTP as phosphatedonors.Kinase activationFig. 12-7
View Full Document