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Stochastic high‐speed rotation of Escherichia coli ATP synthase F 1 sector: the ε subunit‐sensitive rotation
Author(s) -
NakanishiMatsui Mayumi,
Kashiwagi Sachiko,
Hosokawa Hiroyuki,
Cipriano Daniel J.,
Dunn Stanley D.,
Wada Yoh,
Futai Masamitsu
Publication year - 2006
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.20.4.a42-b
Subject(s) - atp synthase , atpase , atp hydrolysis , protein subunit , allosteric regulation , chemistry , random hexamer , rotation (mathematics) , f atpase , kinetics , enzyme , steady state (chemistry) , biophysics , molecule , crystallography , stereochemistry , biochemistry , biology , physics , organic chemistry , mathematics , geometry , thylakoid , chloroplast , quantum mechanics , gene
The γ subunit of the ATP synthase F 1 sector rotates at the center of the α 3 β 3 hexamer during ATP hydrolysis. A gold bead (40 ~ 200 nm diameter) was attached to the γ subunit of E. coli F 1 , and then its ATP hydrolysis‐dependent rotation was studied. The rotation speeds were variable, showing stochastic fluctuation. The high‐speed rates of 40 nm and 60 nm beads were essentially similar: 721 and 671 rps (revolutions/second), respectively. The average rate of 60 nm beads was 381 rps, which is ~ 13‐fold faster than that expected from the steady‐state ATPase turnover number. These results indicate that the F 1 sector rotates much faster than expected from bulk ATPase activity, and that ~ 10 % of F 1 molecules are active on the m sec time scale. Furthermore, the real ATP turnover number (number of ATP molecules converted to ADP and phosphate per sec), as a single molecule, is variable during a short period. The ε subunit inhibited rotation and ATPase whereas ε fused through its carboxyl‐terminus to cytochrome b 562 showed no effect. The ε significantly increased the pausing time during the rotation. Stochastic fluctuation of the catalysis may be a general property of an enzymes, although its understanding requires combining studies of steady‐state kinetics and single molecule observation.