Abstract

The F(1)F(0) ATP synthase is a reversible molecular motor that employs a rotary catalytic cycle to couple a chemiosmotic membrane potential to the formation/hydrolysis of ATP. The multisubunit enzyme contains two copies of the b subunit that form a homodimer as part of a narrow, peripheral stalk structure that connects the membrane (F(0)) and soluble (F(1)) sectors. The three-dimensional structure of the b subunit is unknown making the nature of any interactions or conformational changes within the F(1)F(0) complex difficult to interpret. We have used circular dichroism and analytical ultracentrifugation analyses of a series of N- and C-terminal truncated b proteins to investigate its stability and structure. Thermal denaturation of the b constructs exhibited distinct two-state, cooperative unfolding with T(m) values between 30 and 40 degrees C. CD spectra for the region comprising residues 53-122 (b(53-122)) showed theta;(222)/theta;(208) = 0.99, which reduced to 0.92 in the presence of the hydrophobic solvent trifluoroethanol. Thermodynamic parameters for b(53-122) (DeltaG, DeltaH and DeltaC(p)) were similar to those reported for several nonideal, coiled-coil proteins. Together these results are most consistent with a noncanonical and unstable parallel coiled-coil at the interface of the b dimer. Study holds ProTherm entries: 14865, 14866, 14867, 14868, 14869, 14870, 14871, 14872, 14873, 14874 Extra Details: Residue b24-156. The entire soluble region of the b subunit lacking only the leading 23 residues proposed to span the membrane. protein domains; coiled-coil: thermal denaturation; circular dichroism;,ultracentrifugation

Submission Details

ID: FH7ZeeKo

Submitter: Connie Wang

Submission Date: April 24, 2018, 8:45 p.m.

Version: 1

Publication Details

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