Stability of Water-Soluble Chlorophyll Protein (WSCP) Depends on Phytyl Conformation

Abstract

Water-soluble chlorophyll proteins (WSCP) from Brassicaceae form homotetrameric chlorophyll (Chl)–protein complexes binding one Chl per apoprotein and no carotenoids. Despite the lack of photoprotecting pigments, the complex-bound Chls displays a remarkable stability toward photodynamic damage. On the basis of a mutational study, we show that not only the presence of the phytyls is necessary for photoprotection in WSCPs, as we previously demonstrated, but also is their correct conformation and localization. The extreme heat stability of WSCP also depends on the presence of the phytyl chains, confirming their relevance for the unusual stability of WSCP.

Spectral tuning of chlorophylls in proteins – electrostatics vs. ring deformation

“…An important advantage of using type II WSCPs for studying spectral tuning is the ability to rigorously modify the protein environment of the Chls by assembling them in vitro with recombinantly expressed proteins [21][22][23][24] . By implementing this strategy, Bednarczyk et al 19 demonstrated a spectral tuning mechanism based on a single-point mutation accounting for two-thirds of the spectral shifts between CaWSCP, and LvWSCP.…”

How water-mediated hydrogen bonds affect chlorophyll a/b selectivity in Water-Soluble Chlorophyll Protein

“…4c) in Raman spectra. This interaction is expected not only to contribute to the stabilization of the complex 45 , but also to be the origin of the marked Chl b selectivity displayed by this WSCP variant 17 . This is analogous to the case of the light-harvesting 2 complex (LH2) of purple phototrophic bacterium Rhodobacter sphaeroides , in which an arginine residue has been proven to play a crucial role in binding specificity of the complex, by providing a hydrogen-bond to the C-3 1 acetyl group of the native pigment (bacteriochlorophyll a ) 46 .…”

Asymmetry in the Qy Fluorescence and Absorption Spectra of Chlorophyll a Pertaining to Exciton Dynamics

“…Ground and Q y excited-state optimized structures for Chl-a, modified with methyl replacing phytyl, are evaluated by the CAM-B3LYP (Yanai et al, 2004 ), MN15 (Yu et al, 2016 ), ωB97xD (Chai and Head-Gordon, 2008 ), and B3LYP (Becke, 1993 ) methods using Gaussian-16 (Frisch et al, 2016 ) with the 6-31G * basis set (Hehre et al, 1972 ). Replacement of phytyl with methyl is not expected to have noticeable influences on the properties of interest herein, although its replacement with H (making a carboxylic acid) can be influential (Fiedor et al, 2003 , 2008 ; Palm et al, 2019 ). Also, the choice of basis set has a small influence (Rätsep et al, 2011 ), but as this is much less than the effect of solvent variation, it is not pursued herein.…”