The crystal structure of elongation factor EF-Tu from Thermus aquaticus in the GTP conformation.
BACKGROUND
Elongation factor Tu (EF-Tu) is a GTP-binding protein that is crucial for protein biosynthesis. In the GTP form of the molecule, EF-Tu binds tightly to aminoacyl-tRNA, forming a ternary complex that interacts with the ribosomal acceptor site. During this interaction, GTP is hydrolyzed, and EF-Tu.GDP is ejected.


RESULTS
The crystal structure of EF-Tu from Thermus aquaticus, complexed to the GTP analogue GDPNP, has been determined at 2.5 A resolution and compared to the structure of Escherichia coli EF-Tu.GDP. During the transition from the GDP (inactive) to the GTP (active) form, domain 1, containing the GTP-binding site, undergoes internal conformational changes similar to those observed in ras-p21. In addition, a dramatic rearrangement of domains is observed, corresponding to a rotation of 90.8 degrees of domain 1 relative to domains 2 and 3. Residues that are affected in the binding of aminoacyl-tRNA are found in or near the cleft formed by the domain interface.


CONCLUSIONS
GTP binding by EF-Tu leads to dramatic conformational changes which expose the tRNA binding site. It appears that tRNA binding to EF-Tu induces a further conformational change, which may affect the GTPase activity.
Kjeldgaard
M
M
Department of Chemistry, Aarhus University, Denmark.
Nissen
P
P
Thirup
S
S
Nyborg
J
J
D000595:Amino Acid Sequence; D018360:Crystallography, X-Ray / Q000379:methods; D004926:Escherichia coli / Q000378:metabolism; D006160:Guanosine Triphosphate / Q000031:analogs & derivatives / Q000737:chemistry / Q000378:metabolism*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010444:Peptide Elongation Factor Tu / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism; D017433:Protein Structure, Secondary; D017386:Sequence Homology, Amino Acid; D012984:Software; D013824:Thermus / Q000378:metabolism*
D006160:Guanosine Triphosphate; D010444:Peptide Elongation Factor Tu