Contessi S, Bald D, Baeuerlein E, Dabbeni-Sala F, Mavelli I, Lippe G
Department of Biomedical Sciences and Technologies, University of Udine, p.le Kolbe 4, Udine, 33100, Italy.
Biochem Biophys Res Commun. 2001 Mar;281(5):1266-70. doi: 10.1006/bbrc.2001.4509.
Isolated alpha- and beta-subunits of Thermophilic Bacillus PS3 F(1)ATPase (TF(1)) bind about 1 Fe(III) equivalent. Upon reassembling in the symmetric alpha(3)beta(3) hexamer, Fe(III) binding capacity decreases, as this complex binds about three Fe(III) equivalents. In accordance, when the hexamer is dissociated in the alpha(1)beta(1) heterodimer, each heterodimer binds about one Fe(III) equivalent. On the contrary, native TF(1) exhibits a single Fe(III) site. CD spectra in far UV indicate that upon Fe(III) binding both the whole complex and the isolated beta-subunit undergo structural modifications accompanied by decrease of alpha-helix content, while alpha-subunit doesn't. As in alpha(3)beta(3) and in the whole enzyme the number of bound Fe(III) equivalents is consistent with the number of beta-subunits in the "empty" conformation, it is inferred that the single Fe(III) site in TF(1) is probably located in beta(E).
嗜热芽孢杆菌PS3 F₁ATP酶（TF₁）的分离α亚基和β亚基结合约1个铁（III）当量。在重新组装成对称的α₃β₃六聚体时，铁（III）结合能力下降，因为该复合物结合约3个铁（III）当量。相应地，当六聚体解离成α₁β₁异二聚体时，每个异二聚体结合约1个铁（III）当量。相反，天然TF₁表现出一个单一的铁（III）位点。远紫外区的圆二色光谱表明，铁（III）结合时，整个复合物和分离的β亚基都发生结构修饰，同时α-螺旋含量降低，而α亚基则不然。由于在α₃β₃和整个酶中结合的铁（III）当量数与“空”构象中的β亚基数一致，因此推断TF₁中的单一铁（III）位点可能位于β（E）中。
