The structure of elongation factor G in complex with GDP: conformational flexibility and nucleotide exchange.
BACKGROUND
Elongation factor G (EF-G) catalyzes the translocation step of translation. During translocation EF-G passes through four main conformational states: the GDP complex, the nucleotide-free state, the GTP complex, and the GTPase conformation. The first two of these conformations have been previously investigated by crystallographic methods.


RESULTS
The structure of EF-G-GDP has been refined at 2.4 A resolution. Comparison with the nucleotide-free structure reveals that, upon GDP release, the phosphate-binding loop (P-loop) adopts a closed conformation. This affects the position of helix CG, the switch II loop and domains II, IV and V. Asp83 has a conformation similar to the conformation of the corresponding residue in the EF-Tu/EF-Ts complex. The magnesium ion is absent in EF-G-GDP.


CONCLUSIONS
The results illustrate that conformational changes in the P-loop can be transmitted to other parts of the structure. A comparison of the structures of EF-G and EF-Tu suggests that EF-G, like EF-Tu, undergoes a transition with domain rearrangements. The conformation of EF-G-GDP around the nucleotide-binding site may be related to the mechanism of nucleotide exchange.
al-Karadaghi
S
S
Department of Molecular Biophysics, Lund University, Sweden.
Aevarsson
A
A
Garber
M
M
Zheltonosova
J
J
Liljas
A
A
D001665:Binding Sites / Q000502:physiology; D003461:Crystallography; D020963:GTP Phosphohydrolase-Linked Elongation Factors / Q000737:chemistry; D006153:Guanosine Diphosphate / Q000737:chemistry* / Q000378:metabolism; D008274:Magnesium / Q000378:metabolism; D008958:Models, Molecular; D020653:Peptide Elongation Factor G; D010445:Peptide Elongation Factors / Q000737:chemistry* / Q000378:metabolism; D014176:Protein Biosynthesis / Q000502:physiology; D011487:Protein Conformation; D017434:Protein Structure, Tertiary
D020653:Peptide Elongation Factor G; D010445:Peptide Elongation Factors; D006153:Guanosine Diphosphate; D020963:GTP Phosphohydrolase-Linked Elongation Factors; D008274:Magnesium