title: In vivo phosphorylation and in vitro autophosphorylation-inactivation of Kluyveromyces lactis hexokinase KlHxk1.
abstract: The bifunctional hexokinase KlHxk1 is a key component of glucose-dependent signal transduction in Kluyveromyces lactis. KlHxk1 is phosphorylated in vivo and undergoes ATP-dependent autophosphorylation-inactivation in vitro. This study identifies serine-15 as the site of in vivo phosphorylation and serine-157 as the autophosphorylation-inactivation site. X-ray crystallography of the in vivo phosphorylated enzyme indicates the existence of a ring-shaped symmetrical homodimer carrying two phosphoserine-15 residues. In contrast, small-angle X-ray scattering and equilibrium sedimentation analyses reveal the existence of monomeric phosphoserine-15 KlHxk1 in solution. While phosphorylation at serine-15 and concomitant homodimer dissociation are likely to be involved in glucose signalling, mechanism and putative physiological significance of KlHxk1 inactivation by autophosphorylation at serine-157 remain to be established.
authors.affiliation: Institute of Physiological Chemistry, Carl Gustav Carus Medical Faculty, Technische Universität Dresden, Dresden, Germany. karina.kettner@tu-dresden.de
authors.forename: Karina
authors.initials: K
authors.lastname: Kettner
authors.forename: E Bartholomeus
authors.initials: EB
authors.lastname: Kuettner
authors.forename: Albrecht
authors.initials: A
authors.lastname: Otto
authors.forename: Hauke
authors.initials: H
authors.lastname: Lilie
authors.forename: Ralph P
authors.initials: RP
authors.lastname: Golbik
authors.forename: Norbert
authors.initials: N
authors.lastname: Sträter
authors.forename: Thomas M
authors.initials: TM
authors.lastname: Kriegel
mesh_terms: D004789:Enzyme Activation; D004795:Enzyme Stability; D005947:Glucose / Q000737:chemistry* / Q000378:metabolism*; D006593:Hexokinase / Q000737:chemistry* / Q000378:metabolism* / Q000648:ultrastructure; D007716:Kluyveromyces / Q000145:classification / Q000201:enzymology*; D010766:Phosphorylation; D013045:Species Specificity
chemical_list: D006593:Hexokinase; D005947:Glucose