An alpha to beta conformational switch in EF-Tu.
BACKGROUND
The bacterial elongation factor EF-Tu recognizes and transports aminoacyl-tRNAs to mRNA-programmed ribosomes. EF-Tu shares many structural and functional properties with other GTPases whose conformations are regulated by guanine nucleotides.


RESULTS
An intact form of Escherichia coli EF-Tu complexed with GDP has been crystallized in the presence of the EF-Tu-specific antibiotic GE2270 A. The three-dimensional structure has been solved by X-ray diffraction analysis and refined to a final crystallographic R factor of 17.2% at a resolution of 2.5 A. The location of the GE2270 A antibiotic-binding site could not be identified.


CONCLUSIONS
The structure of EF-Tu-GDP is nearly identical to that of a trypsin-modified form of EF-Tu-GDP, demonstrating conclusively that the protease treatment had not altered any essential structural features. The present structure represents the first view of an ordered Switch I region in EF-Tu-GDP and reveals similarities with two other GTPases complexed with GDP: Ran and ADP-ribosylation factor-1. A comparison of the Switch I regions of the GTP and GDP forms of EF-Tu also reveals that a segment, six amino acids in length, completely converts from an alpha helix in the GTP complex to beta secondary structure in the GDP form. The alpha to beta switch in EF-Tu may represent a prototypical activation mechanism for other protein families.
Abel
K
K
Department of Biochemistry, University of California, Riverside, CA 92521-0129, USA.
Yoder
M D
MD
Hilgenfeld
R
R
Jurnak
F
F
D000900:Anti-Bacterial Agents / Q000737:chemistry*; D001426:Bacterial Proteins / Q000737:chemistry*; D018360:Crystallography, X-Ray; D004926:Escherichia coli; D020963:GTP Phosphohydrolase-Linked Elongation Factors / Q000737:chemistry; D006153:Guanosine Diphosphate / Q000737:chemistry*; D006160:Guanosine Triphosphate / Q000737:chemistry; D010444:Peptide Elongation Factor Tu / Q000737:chemistry*; D010456:Peptides, Cyclic / Q000737:chemistry*; D011487:Protein Conformation; D013045:Species Specificity; D013844:Thiazoles / Q000737:chemistry
D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D010456:Peptides, Cyclic; D013844:Thiazoles; D006153:Guanosine Diphosphate; D006160:Guanosine Triphosphate; D020963:GTP Phosphohydrolase-Linked Elongation Factors; D010444:Peptide Elongation Factor Tu; C068122:GE 2270 A