title: Interaction of mitochondrial elongation factor Tu with aminoacyl-tRNA and elongation factor Ts.
abstract: Elongation factor (EF) Tu promotes the binding of aminoacyl-tRNA (aa-tRNA) to the acceptor site of the ribosome. This process requires the formation of a ternary complex (EF-Tu.GTP.aa-tRNA). EF-Tu is released from the ribosome as an EF-Tu.GDP complex. Exchange of GDP for GTP is carried out through the formation of a complex with EF-Ts (EF-Tu.Ts). Mammalian mitochondrial EF-Tu (EF-Tu(mt)) differs from the corresponding prokaryotic factors in having a much lower affinity for guanine nucleotides. To further understand the EF-Tu(mt) subcycle, the dissociation constants for the release of aa-tRNA from the ternary complex (K(tRNA)) and for the dissociation of the EF-Tu.Ts(mt) complex (K(Ts)) were investigated. The equilibrium dissociation constant for the ternary complex was 18 +/- 4 nm, which is close to that observed in the prokaryotic system. The kinetic dissociation rate constant for the ternary complex was 7.3 x 10(-)(4) s(-)(1), which is essentially equivalent to that observed for the ternary complex in Escherichia coli. The binding of EF-Tu(mt) to EF-Ts(mt) is mutually exclusive with the formation of the ternary complex. K(Ts) was determined by quantifying the effects of increasing concentrations of EF-Ts(mt) on the amount of ternary complex formed with EF-Tu(mt). The value obtained for K(Ts) (5.5 +/- 1.3 nm) is comparable to the value of K(tRNA).
authors.affiliation: Department of Chemistry, University of North Carolina, Chapel Hill, North Carolina 27599-3290, USA.
authors.forename: Y C
authors.initials: YC
authors.lastname: Cai
authors.forename: J M
authors.initials: JM
authors.lastname: Bullard
authors.forename: N L
authors.initials: NL
authors.lastname: Thompson
authors.forename: L L
authors.initials: LL
authors.lastname: Spremulli
mesh_terms: D000818:Animals; D001667:Binding, Competitive; D002417:Cattle; D004926:Escherichia coli / Q000378:metabolism; D006150:Guanine Nucleotides / Q000378:metabolism; D007700:Kinetics; D008930:Mitochondria, Liver / Q000378:metabolism*; D010444:Peptide Elongation Factor Tu / Q000378:metabolism*; D010445:Peptide Elongation Factors / Q000378:metabolism*; D011073:Polyamines; D014176:Protein Biosynthesis; D011487:Protein Conformation; D012360:RNA, Transfer, Phe / Q000378:metabolism*; D016601:RNA-Binding Proteins / Q000378:metabolism; D012270:Ribosomes / Q000378:metabolism
chemical_list: D006150:Guanine Nucleotides; D010445:Peptide Elongation Factors; D011073:Polyamines; D012360:RNA, Transfer, Phe; D016601:RNA-Binding Proteins; C023512:elongation factor Ts; D010444:Peptide Elongation Factor Tu