AUTHOR=Moldenhauer Marcus , Tseng Hsueh-Wei , Kraskov Anastasia , Tavraz Neslihan N. , Yaroshevich Igor A. , Hildebrandt Peter , Sluchanko Nikolai N. , Hochberg Georg A. , Essen Lars-Oliver , Budisa Nediljko , Korf Lukas , Maksimov Eugene G. , Friedrich Thomas
TITLE=Parameterization of a single H-bond in Orange Carotenoid Protein by atomic mutation reveals principles of evolutionary design of complex chemical photosystems
JOURNAL=Frontiers in Molecular Biosciences
VOLUME=10
YEAR=2023
URL=https://www.frontiersin.org/journals/molecular-biosciences/articles/10.3389/fmolb.2023.1072606
DOI=10.3389/fmolb.2023.1072606
ISSN=2296-889X
ABSTRACT=Introduction: Dissecting the intricate networks of covalent and non-covalent interactions that stabilize complex protein structures is notoriously difficult and requires subtle atomic-level exchanges to precisely affect local chemical functionality. The function of the Orange Carotenoid Protein (OCP), a light-driven photoswitch involved in cyanobacterial photoprotection, depends strongly on two H-bonds between the 4-ketolated xanthophyll cofactor and two highly conserved residues in the C-terminal domain (Trp288 and Tyr201).
Method: By orthogonal translation, we replaced Trp288 in Synechocystis OCP with 3-benzothienyl-L-alanine (BTA), thereby exchanging the imino nitrogen for a sulphur atom.
Results: Although the high-resolution (1.8 Å) crystal structure of the fully photoactive OCP-W288_BTA protein showed perfect isomorphism to the native structure, the spectroscopic and kinetic properties changed distinctly. We accurately parameterized the effects of the absence of a single H-bond on the spectroscopic and thermodynamic properties of OCP photoconversion and reveal general principles underlying the design of photoreceptors by natural evolution.
Discussion: Such “molecular surgery” is superior over trial-and-error methods in hypothesis-driven research of complex chemical systems.