Crystal structure of yeast initiation factor 4A, a DEAD-box RNA helicase.
The eukaryotic translation initiation factor 4A (eIF4A) is a member of the DEA(D/H)-box RNA helicase family, a diverse group of proteins that couples an ATPase activity to RNA binding and unwinding. Previous work has provided the structure of the amino-terminal, ATP-binding domain of eIF4A. Extending those results, we have solved the structure of the carboxyl-terminal domain of eIF4A with data to 1.75 A resolution; it has a parallel alpha-beta topology that superimposes, with minor variations, on the structures and conserved motifs of the equivalent domain in other, distantly related helicases. Using data to 2.8 A resolution and molecular replacement with the refined model of the carboxyl-terminal domain, we have completed the structure of full-length eIF4A; it is a "dumbbell" structure consisting of two compact domains connected by an extended linker. By using the structures of other helicases as a template, compact structures can be modeled for eIF4A that suggest (i) helicase motif IV binds RNA; (ii) Arg-298, which is conserved in the DEA(D/H)-box RNA helicase family but is absent from many other helicases, also binds RNA; and (iii) motifs V and VI "link" the carboxyl-terminal domain to the amino-terminal domain through interactions with ATP and the DEA(D/H) motif, providing a mechanism for coupling ATP binding and hydrolysis with conformational changes that modulate RNA binding.
Caruthers
J M
JM
Department of Structural Biology, Stanford University School of Medicine, Stanford, CA 94305, USA.
Johnson
E R
ER
McKay
D B
DB
D000595:Amino Acid Sequence; D018360:Crystallography, X-Ray; D039601:Eukaryotic Initiation Factor-4A; D008958:Models, Molecular; D010448:Peptide Initiation Factors / Q000737:chemistry*; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D020365:RNA Helicases / Q000737:chemistry*; D012441:Saccharomyces cerevisiae / Q000201:enzymology
D010448:Peptide Initiation Factors; D039601:Eukaryotic Initiation Factor-4A; D020365:RNA Helicases