Effects of mutations in the beta subunit hinge domain on ATP synthase F1 sector rotation: interaction between Ser 174 and Ile 163.
A complex of gamma, epsilon, and c subunits rotates in ATP synthase (F(o)F(1)) coupling with proton transport. Replacement of betaSer174 by Phe in beta-sheet4 of the beta subunit (betaS174F) caused slow gamma subunit revolution of the F(1) sector, consistent with the decreased ATPase activity [M. Nakanishi-Matsui, S. Kashiwagi, T. Ubukata, A. Iwamoto-Kihara, Y. Wada, M. Futai, Rotational catalysis of Escherichia coli ATP synthase F1 sector. Stochastic fluctuation and a key domain of the beta subunit, J. Biol. Chem. 282 (2007) 20698-20704]. Modeling of the domain including beta-sheet4 and alpha-helixB predicted that the mutant betaPhe174 residue undergoes strong and weak hydrophobic interactions with betaIle163 and betaIle166, respectively. Supporting this prediction, the replacement of betaIle163 in alpha-helixB by Ala partially suppressed the betaS174F mutation: in the double mutant, the revolution speed and ATPase activity recovered to about half of the levels in the wild-type. Replacement of betaIle166 by Ala lowered the revolution speed and ATPase activity to the same levels as in betaS174F. Consistent with the weak hydrophobic interaction, betaIle166 to Ala mutation did not suppress betaS174F. Importance of the hinge domain [phosphate-binding loop (P-loop)/alpha-helixB/loop/beta-sheet4, betaPhe148-betaGly186] as to driving rotational catalysis is discussed.
Kashiwagi
Sachiko
S
Department of Biochemistry, Faculty of Pharmaceutical Sciences, Iwate Medical University, Iwate 028-3694, Japan.
Iwamoto-Kihara
Atsuko
A
Kojima
Masaki
M
Nonaka
Takamasa
T
Futai
Masamitsu
M
Nakanishi-Matsui
Mayumi
M
D020409:Molecular Motor Proteins / Q000737:chemistry* / Q000648:ultrastructure*; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D021122:Protein Subunits; D006180:Proton-Translocating ATPases / Q000737:chemistry* / Q000648:ultrastructure*; D012399:Rotation; D013329:Structure-Activity Relationship
D020409:Molecular Motor Proteins; D021122:Protein Subunits; D006180:Proton-Translocating ATPases