Phosphorylation of elongation factor Tu prevents ternary complex formation.
The elongation factor Tu (EF-Tu) is a member of the GTP/GDP-binding proteins and interacts with various partners during the elongation cycle of protein biosynthesis thereby mediating the correct binding of amino-acylated transfer RNA (aa-tRNA) to the acceptor site (A-site) of the ribosome. After GTP hydrolysis EF-Tu is released in its GDP-bound state. In vivo, EF-Tu is post-translationally modified by phosphorylation. Here we report that the phosphorylation of EF-Tu by a ribosome associated kinase activity is drastically enhanced by EF-Ts. The antibiotic kirromycin, known to block EF-Tu function, inhibits the modification. This effect is specific, since kirromycin-resistant mutants do become phosphorylated in the presence of the antibiotic. On the other hand, phosphorylated wild-type EF-Tu does not bind kirromycin. Most interestingly, the phosphorylation of EF-Tu abolishes its ability to bind aa-tRNA. In the GTP conformation the site of modification is located at the interface between domains 1 and 3 and is involved in a strong interdomain hydrogen bond. Introduction of a charged phosphate group at this position will change the interaction between the domains, leading to an opening of the molecule reminiscent of the GDP conformation. A model for the function of EF-Tu phosphorylation in protein biosynthesis is presented.
Alexander
C
C
Institut für Biochemie, Freie Universität Berlin, Dahlem, Germany.
Bilgin
N
N
Lindschau
C
C
Mesters
J R
JR
Kraal
B
B
Hilgenfeld
R
R
Erdmann
V A
VA
Lippmann
C
C
D000900:Anti-Bacterial Agents / Q000378:metabolism; D003196:Computer Graphics; D004926:Escherichia coli / Q000378:metabolism; D008958:Models, Molecular; D010444:Peptide Elongation Factor Tu / Q000737:chemistry / Q000378:metabolism*; D010445:Peptide Elongation Factors / Q000378:metabolism; D010766:Phosphorylation; D011487:Protein Conformation; D011499:Protein Processing, Post-Translational; D011728:Pyridones / Q000378:metabolism; D012346:RNA, Transfer, Amino Acyl / Q000378:metabolism
D000900:Anti-Bacterial Agents; D010445:Peptide Elongation Factors; D011728:Pyridones; D012346:RNA, Transfer, Amino Acyl; C023512:elongation factor Ts; D010444:Peptide Elongation Factor Tu; C008536:mocimycin