8hn3

Publication Abstract from PubMed

In photosynthetic green sulfur bacteria, the electron transfer reaction from menaquinol:cytochrome c oxidoreductase to the P840 reaction center (RC) complex occurs directly without any involvement of soluble electron carrier protein(s). X-ray crystallography has determined the three-dimensional structures of the soluble domains of the CT0073 gene product and Rieske iron-sulfur protein (ISP). The former is a mono-heme cytochrome c with an alpha-absorption peak at 556 nm. The overall fold of the soluble domain of cytochrome c-556 (designated as cyt c-556(sol)) consists of four alpha-helices and is very similar to that of water-soluble cyt c-554 that independently functions as an electron donor to the P840 RC complex. However, the latter's remarkably long and flexible loop between the alpha3 and alpha4 helices seems to make it impossible to be a substitute for the former. The structure of the soluble domain of the Rieske ISP (Rieske(sol) protein) shows a typical beta-sheets-dominated fold with a small cluster-binding and a large subdomain. The architecture of the Rieske(sol) protein is bilobal and belongs to those of b(6)f-type Rieske ISPs. Nuclear magnetic resonance (NMR) measurements revealed weak non-polar but specific interaction sites on Rieske(sol) protein when mixed with cyt c-556(sol). Therefore, menaquinol:cytochrome c oxidoreductase in green sulfur bacteria features a Rieske/cytb complex tightly associated with membrane-anchored cyt c-556.

Soluble domains of cytochrome c-556 and Rieske iron-sulfur protein from Chlorobaculum tepidum: Crystal structures and interaction analysis.,Kishimoto H, Azai C, Yamamoto T, Mutoh R, Nakaniwa T, Tanaka H, Miyanoiri Y, Kurisu G, Oh-Oka H Curr Res Struct Biol. 2023 Apr 19;5:100101. doi: 10.1016/j.crstbi.2023.100101. , eCollection 2023. PMID:37180033^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.