Mössbauer spectroscopy and DFT calculations on all protonation states of the 2Fe-2S cluster of the Rieske protein

摘要: The Thermus thermophilus Rieske protein (TtRP) contains a 2Fe-2S cluster with one iron (Fe-Cys) coordinated by four sulfur atoms (2xS2− and 2xCys) (Fe-His) two nitrogen (2xS2−, His134 His154). Here, the is investigated at three pH values (6.0, 8.5 10.5) in order to elucidate protonation states of His-ligands. Examination effect on electronic structure via Mossbauer spectroscopy gives deeper understanding coupling electron transfer state Two components (1 referring Fe-Cys 2 Fe-His) parameters typical for diamagnetic [2Fe-2S]2+ are detected. clearly correlate: while δ remains almost pH-independent 1 (pH6.0) = 0.23 (± 0.01) mms− (pH10.5) 0.24 Fe-Cys, it decreases Fe-His from 0.34 0.28 1. ΔE Q changes Q1 0.57 0.45 Q2 1.05 0.71 Density functional theory (DFT)-calculations based crystal (pdb 1NYK) (Hunsicker-Wang et al. Biochemistry 42, 7303, 2003) have been performed Rieske-cluster different His-ligand states, reproducing experimentally observed trend.