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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 ?-subunits and the rotor ?-subunit. The ?-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 ?-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-? 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 ? is not involved in cooperative interplays between the catalytic ?-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 ?-subunit was less tightly held in the ?(3)?(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 ?-helix in the alanine mutant. Our results emphasize the importance of loop rigidity for efficient torque transmissions.

SUBMITTER: Tanigawara M 

PROVIDER: S-EPMC3433597 | BioStudies | 2012-01-01

REPOSITORIES: biostudies

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