title: Role of the DELSEED loop in torque transmission of F1-ATPase.
abstract: F(1)-ATPase is an ATP-driven rotary motor that generates torque at the interface between the catalytic β-subunits and the rotor γ-subunit. The β-subunit inwardly rotates the C-terminal domain upon nucleotide binding/dissociation; hence, the region of the C-terminal domain that is in direct contact with γ-termed the DELSEED loop-is thought to play a critical role in torque transmission. We substituted all the DELSEED loop residues with alanine to diminish specific DELSEED loop-γ interactions and with glycine to disrupt the loop structure. All the mutants rotated unidirectionally with kinetic parameters comparable to those of the wild-type F(1), suggesting that the specific interactions between DELSEED loop and γ is not involved in cooperative interplays between the catalytic β-subunits. Glycine substitution mutants generated half the torque of the wild-type F(1), whereas the alanine mutant generated comparable torque. Fluctuation analyses of the glycine/alanine mutants revealed that the γ-subunit was less tightly held in the α(3)β(3)-stator ring of the glycine mutant than in the wild-type F(1) and the alanine mutant. Molecular dynamics simulation showed that the DELSEED loop was disordered by the glycine substitution, whereas it formed an α-helix in the alanine mutant. Our results emphasize the importance of loop rigidity for efficient torque transmissions.
authors.affiliation: Graduate School of Frontier Bioscience, Osaka University, Osaka, Japan.
authors.forename: Mizue
authors.initials: M
authors.lastname: Tanigawara
authors.forename: Kazuhito V
authors.initials: KV
authors.lastname: Tabata
authors.forename: Yuko
authors.initials: Y
authors.lastname: Ito
authors.forename: Jotaro
authors.initials: J
authors.lastname: Ito
authors.forename: Rikiya
authors.initials: R
authors.lastname: Watanabe
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Ueno
authors.forename: Mitsunori
authors.initials: M
authors.lastname: Ikeguchi
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Noji
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D001407:Bacillus / Q000201:enzymology; D007700:Kinetics; D056004:Molecular Dynamics Simulation; D008969:Molecular Sequence Data; D009154:Mutation; D017434:Protein Structure, Tertiary; D006180:Proton-Translocating ATPases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D012399:Rotation; D019415:Torque
chemical_list: D006180:Proton-Translocating ATPases