title: Crystal structure of highly thermostable glycerol kinase from a hyperthermophilic archaeon in a dimeric form.
abstract: The crystal structure of glycerol kinase from the hyperthermophilic archaeon Thermococcus kodakaraensis (Tk-GK) in a dimeric form was determined at a resolution of 2.4 A. This is the first crystal structure of a hyperthermophilic glycerol kinase. The overall structure of the Tk-GK dimer is very similar to that of the Escherichia coli glycerol kinase (Ec-GK) dimer. However, two dimers of Ec-GK can associate into a tetramer with a twofold axis, whereas those of Tk-GK cannot. This may be the reason why Tk-GK is not inhibited by fructose 1,6-bisphosphate, because the fructose 1,6-bisphosphate binding site is produced only when a tetrameric structure is formed. Differential scanning calorimetry analyses indicate that Tk-GK is a highly thermostable protein with a melting temperature (T(m)) of 105.4 degrees C for the major transition. This value is higher than that of Ec-GK by 34.1 degrees C. Comparison of the crystal structures of Tk-GK and Ec-GK indicate that there is a marked difference in the number of ion pairs in the alpha16 helix. Four ion pairs, termed IP1-IP4, are formed in this helix in the Tk-GK structure. To examine whether these ion pairs contribute to the stabilization of Tk-GK, four Tk-GK and four Ec-GK derivatives with reciprocal mutations at the IP1-IP4 sites were constructed. The determination of their stabilities indicates that the removal of each ion pair does not affect the stability of Tk-GK significantly, whereas the mutations designed to introduce one of these ion pairs stabilize or destabilize Ec-GK considerably. These results suggest that the ion pairs in the alpha16 helix contribute to the stabilization of Tk-GK in a cooperative manner.
authors.affiliation: Department of Material and Life Science, Graduate School of Engineering, Osaka University, Suita, Osaka, Japan.
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Koga
authors.forename: Ryota
authors.initials: R
authors.lastname: Katsumi
authors.forename: Dong-Ju
authors.initials: DJ
authors.lastname: You
authors.forename: Hiroyoshi
authors.initials: H
authors.lastname: Matsumura
authors.forename: Kazufumi
authors.initials: K
authors.lastname: Takano
authors.forename: Shigenori
authors.initials: S
authors.lastname: Kanaya
mesh_terms: D000595:Amino Acid Sequence; D019843:Archaeal Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D001665:Binding Sites; D018360:Crystallography, X-Ray; D019281:Dimerization; D004795:Enzyme Stability; D029968:Escherichia coli Proteins / Q000737:chemistry; D005991:Glycerol Kinase / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011487:Protein Conformation; D021122:Protein Subunits / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D013696:Temperature; D019712:Thermococcus / Q000201:enzymology*
chemical_list: D019843:Archaeal Proteins; D029968:Escherichia coli Proteins; D021122:Protein Subunits; D005991:Glycerol Kinase