Structure and flexibility of the C-ring in the electromotor of rotary F(0)F(1)-ATPase of pea chloroplasts.
A ring of 8-15 identical c-subunits is essential for ion-translocation by the rotary electromotor of the ubiquitous F(O)F(1)-ATPase. Here we present the crystal structure at 3.4Å resolution of the c-ring from chloroplasts of a higher plant (Pisum sativum), determined using a native preparation. The crystal structure was found to resemble that of an (ancestral) cyanobacterium. Using elastic network modeling to investigate the ring's eigen-modes, we found five dominant modes of motion that fell into three classes. They revealed the following deformations of the ring: (I) ellipsoidal, (II) opposite twisting of the luminal circular surface of the ring against the stromal surface, and (III) kinking of the hairpin-shaped monomers in the middle, resulting in bending/stretching of the ring. Extension of the elastic network analysis to rings of different c(n)-symmetry revealed the same classes of dominant modes as in P. sativum (c(14)). We suggest the following functional roles for these classes: The first and third classes of modes affect the interaction of the c-ring with its counterparts in F(O), namely subunits a and bb'. These modes are likely to be involved in ion-translocation and torque generation. The second class of deformation, along with deformations of subunits γ and ε might serve to elastically buffer the torque transmission between F(O) and F(1).
Department of Biochemistry and Molecular Biology, George S. Wise Faculty of Life Sciences, Tel-Aviv University, Ramat Aviv, Israel.
Shai
S
Saroussi
Maya
M
Schushan
Nir
N
Ben-Tal
Wolfgang
W
Junge
Nathan
N
Nelson
D000595:Amino Acid Sequence; D025222:Chloroplast Proton-Translocating ATPases / Q000737:chemistry*; D002736:Chloroplasts / Q000737:chemistry*; D018360:Crystallography, X-Ray; D000458:Cyanobacteria / Q000737:chemistry; D004926:Escherichia coli / Q000737:chemistry; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009038:Motion; D018532:Pisum sativum / Q000737:chemistry*; D010940:Plant Proteins / Q000737:chemistry*; D011487:Protein Conformation; D021122:Protein Subunits / Q000737:chemistry*; D011522:Protons; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid
D010940:Plant Proteins; D021122:Protein Subunits; D011522:Protons; D025222:Chloroplast Proton-Translocating ATPases