The structure of the chloroplast F1-ATPase at 3.2 A resolution.
The structure of the F(1)-ATPase from spinach chloroplasts was determined to 3.2 A resolution by molecular replacement based on the homologous structure of the bovine mitochondrial enzyme. The crystallized complex contains four different subunits in a stoichiometry of alpha(3)beta(3)gammaepsilon. Subunit delta was removed before crystallization to improve the diffraction of the crystals. The overall structure of the noncatalytic alpha-subunits and the catalytic beta-subunits is highly similar to those of the mitochondrial and thermophilic subunits. However, in the crystal structure of the chloroplast enzyme, all alpha- and beta-subunits adopt a closed conformation and appear to contain no bound adenine nucleotides. The superimposed crystallographic symmetry in the space group R32 impaired an exact tracing of the gamma- and epsilon-subunits in the complex. However, clear electron density was present at the core of the alpha(3)beta(3)-subcomplex, which probably represents the C-terminal domain of the gamma-subunit. The structure of the spinach chloroplast F(1) has a potential binding site for the phytotoxin, tentoxin, at the alphabeta-interface near betaAsp(83) and an insertion from betaGly(56)-Asn(60) in the N-terminal beta-barrel domain probably increases the thermal stability of the complex. The structure probably represents an inactive latent state of the ATPase, which is unique to chloroplast and cyanobacterial enzymes.
Groth
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Heinrich-Heine-Universität, Biochemie der Pflanzen, Universitätsstrasse 1, D-40225 Düsseldorf, Germany and EMBL Hamburg, Notkestrasse 85, D-22603 Hamburg, Germany. georg.groth@uniduesseldorf.de
Pohl
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D000818:Animals; D002417:Cattle; D002736:Chloroplasts / Q000201:enzymology*; D018360:Crystallography, X-Ray; D019281:Dimerization; D008928:Mitochondria / Q000201:enzymology; D008958:Models, Molecular; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D021122:Protein Subunits; D006180:Proton-Translocating ATPases / Q000737:chemistry*; D018724:Spinacia oleracea / Q000201:enzymology; D013816:Thermodynamics
D021122:Protein Subunits; D006180:Proton-Translocating ATPases