title: Tighter αC-helix-αL16-helix interactions seem to make p38α less prone to activation by autophosphorylation than Hog1.
abstract: Many eukaryotic protein kinases (EPKs) are autoactivated through autophosphorylation of their activation loop. Mitogen-activated protein (MAP) kinases do not autophosphorylate spontaneously; relying instead upon mitogen-activated protein kinase (MAPK) kinases (MKKs) for their activation loop phosphorylation. Yet, in previous studies we identified mutations in the yeast MAPK high osmolarity glycerol (Hog1) that render it capable of spontaneous autophosphorylation and consequently intrinsically active (MKK-independent). Four of the mutations occurred in hydrophobic residues, residing in the αC-helix, which is conserved in all EPKs, and in the αL16-helix that is unique to MAPKs. These four residues interact together forming a structural element termed 'hydrophobic core'. A similar element exists in the Hog1's mammalian orthologues p38s. Here we show that the 'hydrophobic core' is a loose suppressor of Hog1's autophosphorylation. We inserted 18 point mutations into this core, 17 of which were able to render Hog1 MKK-independent. In p38s, however, only a very few mutations in the equivalent residues rendered these proteins intrinsically active. Structural analysis revealed that a salt bridge between the αC-helix and the αL16-helix that exists in p38α may not exist in Hog1. This bond further stabilizes the 'hydrophobic core' of p38, making p38 less prone to de-repressing its concealed autophosphorylation. Mutating equivalent hydrophobic residues in Jnk1 and Erk2 has no effect on their autophosphorylation. We propose that specific structural elements developed in the course of evolution to suppress spontaneous autophosphorylation of Hog1/p38. The suppressors were kept wobbly, probably to allow activation by induced autophosphorylation, but became stricter in mammalian p38s than in the yeast Hog1.
authors.affiliation: Department of Biological Chemistry, The Alexander Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Jerusalem 91904, Israel.
authors.forename: Masha
authors.initials: M
authors.lastname: Tesker
authors.affiliation: Department of Microbiology and Immunology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 117456, Singapore CREATE-NUS-HUJ Cellular and Molecular Mechanisms of Inflammation Programme, National University of Singapore, 1 Create Way, Innovation Wing, #03-09, Singapore 138602, Singapore.
authors.forename: Sadiduddin Edbe
authors.initials: SE
authors.lastname: Selamat
authors.affiliation: Department of Biological Chemistry, The Alexander Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Jerusalem 91904, Israel.
authors.forename: Jonah
authors.initials: J
authors.lastname: Beenstock
authors.affiliation: Department of Biological Chemistry, The Alexander Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Jerusalem 91904, Israel The Wolfson Centre for Applied Structural Biology, The Hebrew University of Jerusalem, Jerusalem 91904, Israel.
authors.forename: Ruchama
authors.initials: R
authors.lastname: Hayouka
authors.affiliation: Department of Biological Chemistry, The Alexander Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Jerusalem 91904, Israel The Wolfson Centre for Applied Structural Biology, The Hebrew University of Jerusalem, Jerusalem 91904, Israel.
authors.forename: Oded
authors.initials: O
authors.lastname: Livnah
authors.affiliation: Department of Biological Chemistry, The Alexander Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Jerusalem 91904, Israel Department of Microbiology and Immunology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 117456, Singapore CREATE-NUS-HUJ Cellular and Molecular Mechanisms of Inflammation Programme, National University of Singapore, 1 Create Way, Innovation Wing, #03-09, Singapore 138602, Singapore engelber@mail.huji.ac.il.
authors.forename: David
authors.initials: D
authors.lastname: Engelberg
mesh_terms: D048308:Mitogen-Activated Protein Kinase 14 / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation; D017433:Protein Structure, Secondary; D012441:Saccharomyces cerevisiae / Q000201:enzymology* / Q000235:genetics; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism
chemical_list: D029701:Saccharomyces cerevisiae Proteins; C088589:HOG1 protein, S cerevisiae; D048308:Mitogen-Activated Protein Kinase 14; D020928:Mitogen-Activated Protein Kinases
keywords: Hog1; MAP kinase; autophosphorylation; hydrophobic core; kinase; p38