Role of the DELSEED Loop in Torque Transmission of F1-ATPase

F1-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 wit...

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Bibliographic Details
Published in:Biophysical journal 2012-09, Vol.103 (5), p.970-978
Main Authors: Tanigawara, Mizue, Tabata, Kazuhito V., Ito, Yuko, Ito, Jotaro, Watanabe, Rikiya, Ueno, Hiroshi, Ikeguchi, Mitsunori, Noji, Hiroyuki
Format: Article
Language:English
Subjects:
alanine
Amino Acid Motifs
Amino Acid Sequence
Amino Acid Substitution
Bacillus - enzymology
direct contact
dissociation
Kinetics
molecular dynamics
Molecular Dynamics Simulation
Molecular Sequence Data
mutants
Mutation
Protein Structure, Tertiary
Proteins and Nucleic Acids
Proton-Translocating ATPases - chemistry
Proton-Translocating ATPases - genetics
Proton-Translocating ATPases - metabolism
Rotation
Torque
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Summary:F1-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 F1, 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 F1, 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 α3β3-stator ring of the glycine mutant than in the wild-type F1 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.
ISSN:0006-3495
1542-0086
DOI:10.1016/j.bpj.2012.06.054