The role of cysteinyl residues in the activity of bacterial elongation factor Ts, a guanosine nucleotide dissociation protein.
The modification of E.coli elongation factor Ts (EF-Ts) by NEM and other sulfhydryl reagents inactivates the protein's ability to bind EF-Tu.GDP and to catalyze GDP exchange. The reactive residue was found to be Cys-22. Replacement of Cys-22 by Ser or Gly only partially impairs the binding or catalytic properties of EF-Ts while it completely protects EF-Ts from the inactivation by NEM. Cys-22 of EF-Ts is not located at the EF-Ts.EF-Tu interface, yet it can be modified only when EF-Ts is not bound to EF-Tu. These results support the proposal that the conformation change around Cys-22 in the amino terminus of EF-Ts rather than Cys-22 itself is essential for binding EF-Tu. Apparently, modification of Cys-22 by NEM disrupts the conformation change and inactivates EF-Ts. The return of EF-Ts to its native conformation may provide the driving force for the rate-determining step in the catalytic cycle, the dissociation of EF-Ts from EF-Tu.GNP.
Hwang
Y W
YW
New York State Institute for Basic Research in Developmental Disabilities, Staten Island 10314, USA.
Sanchez
A
A
Hwang
M C
MC
Miller
D L
DL
D019943:Amino Acid Substitution; D003001:Cloning, Molecular; D003545:Cysteine; D004926:Escherichia coli / Q000378:metabolism*; D005998:Glycine; D006153:Guanosine Diphosphate / Q000378:metabolism*; D007700:Kinetics; D016297:Mutagenesis, Site-Directed; D010445:Peptide Elongation Factors / Q000737:chemistry* / Q000378:metabolism*; D011487:Protein Conformation; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D016324:Sequence Tagged Sites; D012694:Serine
D010445:Peptide Elongation Factors; D011994:Recombinant Proteins; C023512:elongation factor Ts; D006153:Guanosine Diphosphate; D012694:Serine; D003545:Cysteine; D005998:Glycine