title: Water-Soluble Chlorophyll Protein (WSCP) Stably Binds Two or Four Chlorophylls.
abstract: Water-soluble chlorophyll proteins (WSCPs) of class IIa from Brassicaceae form tetrameric complexes containing one chlorophyll (Chl) per apoprotein but no carotenoids. The complexes are remarkably stable toward dissociation and protein denaturation even at 100 °C and extreme pH values, and the Chls are partially protected against photooxidation. There are several hypotheses that explain the biological role of WSCPs, one of them proposing that they function as a scavenger of Chls set free upon plant senescence or pathogen attack. The biochemical properties of WSCP described in this paper are consistent with the protein acting as an efficient and flexible Chl scavenger. At limiting Chl concentrations, the recombinant WSCP apoprotein binds substoichiometric amounts of Chl (two Chls per tetramer) to form complexes that are as stable toward thermal dissociation, denaturation, and photodamage as the fully pigmented ones. If more Chl is added, these two-Chl complexes can bind another two Chls to reach the fully pigmented state. The protection of WSCP Chls against photodamage has been attributed to the apoprotein serving as a diffusion barrier for oxygen, preventing its access to triplet excited Chls and, thus, the formation of singlet oxygen. By contrast, the sequential binding of Chls by WSCP suggests a partially open or at least flexible structure, raising the question of how WSCP photoprotects its Chls without the help of carotenoids.
authors.affiliation: Institute of General Botany, Johannes-Gutenberg University Mainz , Johannes-von-Müller-Weg 6, 55128 Mainz, Germany.
authors.forename: Daniel M
authors.initials: DM
authors.lastname: Palm
authors.affiliation: Institute of General Botany, Johannes-Gutenberg University Mainz , Johannes-von-Müller-Weg 6, 55128 Mainz, Germany.|Department of Chemical Sciences, University of Padova , Via Marzolo 1, 35131 Padova, Italy.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Agostini
authors.affiliation: Institute for Immunology, University Medical Center Mainz , Langenbeckstrasse 1, 55131 Mainz, Germany.
authors.forename: Stefan
authors.initials: S
authors.lastname: Tenzer
authors.affiliation: Institute of General Botany, Johannes-Gutenberg University Mainz , Johannes-von-Müller-Weg 6, 55128 Mainz, Germany.
authors.forename: Barbara M
authors.initials: BM
authors.lastname: Gloeckle
authors.affiliation: Institute of General Botany, Johannes-Gutenberg University Mainz , Johannes-von-Müller-Weg 6, 55128 Mainz, Germany.
authors.forename: Mara
authors.initials: M
authors.lastname: Werwie
authors.affiliation: Department of Chemical Sciences, University of Padova , Via Marzolo 1, 35131 Padova, Italy.
authors.forename: Donatella
authors.initials: D
authors.lastname: Carbonera
authors.affiliation: Institute of General Botany, Johannes-Gutenberg University Mainz , Johannes-von-Müller-Weg 6, 55128 Mainz, Germany.
authors.forename: Harald
authors.identifier: 0000-0003-0532-3004
authors.initials: H
authors.lastname: Paulsen
mesh_terms: D001059:Apoproteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D001937:Brassica / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002734:Chlorophyll / Q000737:chemistry* / Q000378:metabolism; D000077194:Chlorophyll A; D015870:Gene Expression; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D008027:Light; D045342:Light-Harvesting Protein Complexes / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D008958:Models, Molecular; D010084:Oxidation-Reduction; D010100:Oxygen; D018532:Pisum sativum / Q000737:chemistry; D010940:Plant Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D011485:Protein Binding; D011489:Protein Denaturation; D000072417:Protein Domains; D055503:Protein Multimerization; D055550:Protein Stability; D017433:Protein Structure, Secondary; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D026082:Singlet Oxygen; D012995:Solubility; D020524:Thylakoids / Q000737:chemistry / Q000378:metabolism; D014867:Water / Q000737:chemistry
chemical_list: D001059:Apoproteins; D045342:Light-Harvesting Protein Complexes; D010940:Plant Proteins; D011993:Recombinant Fusion Proteins; C115715:WSCP protein, Brassica oleracea; D014867:Water; D002734:Chlorophyll; D026082:Singlet Oxygen; C037184:chlorophyll b; D010100:Oxygen; D000077194:Chlorophyll A