title: Opposite roles of domains 2+3 of Escherichia coli EF-Tu and Bacillus stearothermophilus EF-Tu in the regulation of EF-Tu GTPase activity.
abstract: The effect of noncatalytic domains 2+3 on the intrinsic activity and thermostability of the EF-Tu GTPase center was evaluated in experiments with isolated domains 1 and six chimeric variants of mesophilic Escherichia coli (Ec) and thermophilic Bacillus stearothermophilus (Bst) EF-Tus. The isolated catalytic domains 1 of both EF-Tus displayed similar GTPase activities at their optimal temperatures. However, noncatalytic domains 2+3 of the EF-Tus influenced the GTPase activity of domains 1 differently, depending on the domain origin. Ecdomains 2+3 suppressed the GTPase activity of the Ecdomain 1, whereas those of BstEF-Tu stimulated the Bstdomain 1 GTPase. Domain 1 and domains 2+3 of both EF-Tus positively cooperated to heat-stabilize their GTPase centers to attain optimal activity at a temperature close to the optimal growth temperature of either organism. This can be explained by a stabilization effect of domains 2+3 on alpha-helical regions of the G-domain as revealed by CD spectroscopy.
authors.affiliation: Department of Gene Expression, Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, Flemingovo nám. 2, 166 37 Prague 6, Czech Republic.
authors.forename: Hana
authors.initials: H
authors.lastname: Sanderová
authors.forename: Jirí
authors.initials: J
authors.lastname: Jonák
mesh_terms: D004926:Escherichia coli / Q000235:genetics*; D020558:GTP Phosphohydrolases / Q000378:metabolism*; D001411:Geobacillus stearothermophilus / Q000235:genetics*; D007700:Kinetics; D010444:Peptide Elongation Factor Tu / Q000737:chemistry* / Q000378:metabolism; D011489:Protein Denaturation; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000378:metabolism; D013045:Species Specificity; D013816:Thermodynamics
chemical_list: D011993:Recombinant Fusion Proteins; D020558:GTP Phosphohydrolases; D010444:Peptide Elongation Factor Tu