The binding of eosin‐labeled subunit δ to the isolated chloroplast ATPase, CF1, as revealed by rotational diffusion in solution

FEBS Letters

Junge, Wolfgang¹  Engelbrecht, Siegfried¹  Wagner, Richard¹  Apley, Enno C.¹ 

[1] Biophysik, Fachbereich Biologie/Chemie, Universität Osnabrück, Postfach 4469, D-4500 Osnabrück, FRG

关键词: Photophosphorylation;    ATPase;    Coupling factor;    δ-Subunit;    Rotational diffusion;    CF1 (CF0);    soluble (membrane) portion of the chloroplast ATP synthase;    eosin-NCS;    eosin 5-isothiocyanate;    OSCP;    oligomycin sensitivity-conferring protein of the mitochondrial coupling factor;    PMS;    phenazine methosulfate;   

DOI  :  10.1016/0014-5793(88)80652-5

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

We investigated the binding of subunit δ to solubilized chloroplast ATPase. Purified δ was covalently labeled with eosin 5-isothiocyanate and its rotational correlation time was determined by a photoselection technique as a function of added CF₁ (containing δ) and of CF₁(−δ) (lacking δ). In aqueous buffer the rotational correlation time of labeled δ was 33 ns. This is compatible with a rather elongated shape with the dimensions 2b = 100 Å/2a = 28 Å. Binding of δ to CF₁ decreased the rotational correlation time about 10-fold. The result was a biphasic decay of the laser flash-induced absorption anisotropy which was analyzed to yield the proportion of δ (bound to CF₁) relative to δ (free). CF₁(−δ), which completely lacked the δ-subunit, bound one δ (mol/mol) with high affinity (K _d ≈ 100 nM) and at least another δ with about 20-fold lower affinity. The δ-containing CF₁, revealed only the low-affinity site(s) for δ. This was compatible with a 1:1 stoichiometry of δ in isolated CF₁.

【 授权许可】

Unknown