Site-directed mutagenesis of Thermus thermophilus EF-Tu: the substitution of threonine-62 by serine or alanine.
The invariant threonine-62, which occurs in the effector region of all GTP/GDP-binding regulatory proteins, was substituted via site-directed mutagenesis by alanine and serine in the elongation factor Tu from Thermus thermophilus. The altered proteins were overproduced in Escherichia coli, purified and characterized. The EF-Tu T62S variant had similar properties with respect to thermostability, aminoacyl-tRNA binding, GTPase activity and in vitro translation as the wild-type EF-Tu. In contrast, EF-Tu T62A is severely impaired in its ability to sustain polypeptide synthesis and has only very low intrinsic and ribosome-induced GTPase activity. The affinity of aminoacyl-tRNA to the EF-Tu T62A.GTP complex is almost 40 times lower as compared to the native EF-Tu.GTP. These observations are in agreement with the tertiary structure of EF-Tu.GTP, in which threonine-62 is interacting with the Mg2+ ion, gamma-phosphate of GTP and a water molecule, which is presumably involved in the GTP hydrolysis.
Ahmadian
M R
MR
Laboratorium für Biochemie Universität Bayreuth, Germany.
Kreutzer
R
R
Blechschmidt
B
B
Sprinzl
M
M
D000409:Alanine / Q000378:metabolism; D001483:Base Sequence; D001665:Binding Sites; D017931:DNA Primers; D020963:GTP Phosphohydrolase-Linked Elongation Factors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D006153:Guanosine Diphosphate / Q000378:metabolism; D006160:Guanosine Triphosphate / Q000378:metabolism; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010444:Peptide Elongation Factor Tu / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D012346:RNA, Transfer, Amino Acyl / Q000378:metabolism; D012694:Serine / Q000378:metabolism; D016963:Thermus thermophilus / Q000235:genetics / Q000378:metabolism*; D013912:Threonine / Q000378:metabolism
D017931:DNA Primers; D012346:RNA, Transfer, Amino Acyl; D006153:Guanosine Diphosphate; D013912:Threonine; D012694:Serine; D006160:Guanosine Triphosphate; D020963:GTP Phosphohydrolase-Linked Elongation Factors; D010444:Peptide Elongation Factor Tu; D000409:Alanine