Pigment binding, fluorescence properties, and oligomerization behavior of Lhca5, a novel light-harvesting protein.
A new potential light-harvesting protein, named Lhca5, was recently detected in higher plants. Because of the low amount of Lhca5 in thylakoid membranes, the isolation of a native Lhca5 pigment-protein complex has not been achieved to date. Therefore, we used in vitro reconstitution to analyze whether Lhca5 binds pigments and is actually an additional light-harvesting protein. By this approach we could demonstrate that Lhca5 binds pigments in a unique stoichiometry. Analyses of pigment requirements for light-harvesting complex formation by Lhca5 revealed that chlorophyll b is the only indispensable pigment. Fluorescence measurements showed that ligated chlorophylls and carotenoids are arranged in a way that allows directed energy transfer within the light-harvesting complex. Reconstitutions of Lhca5 together with other Lhca proteins resulted in the formation of heterodimers with Lhca1. This result demonstrates that Lhca5 is indeed a protein belonging to the light-harvesting antenna of photosystem I. The properties of Lhca5 are compared with those of previously characterized Lhca proteins, and the consequences of an additional Lhca protein for the composition of the light-harvesting antenna of photosystem I are discussed in view of the recently published photosystem I structure of the pea.
Storf
Stefanie
S
Institut für Allgemeine Botanik, Johannes Gutenberg-Universität Mainz, Müllerweg 6, 55099 Mainz, Germany.
Jansson
Stefan
S
Schmid
Volkmar H R
VH
D017360:Arabidopsis / Q000737:chemistry* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D002338:Carotenoids / Q000378:metabolism; D002734:Chlorophyll / Q000378:metabolism; D061146:Chlorophyll Binding Proteins; D019281:Dimerization; D005453:Fluorescence; D045342:Light-Harvesting Protein Complexes / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D045331:Photosystem I Protein Complex / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D010860:Pigments, Biological / Q000378:metabolism*; D020836:Protein Structure, Quaternary
D029681:Arabidopsis Proteins; D061146:Chlorophyll Binding Proteins; C490278:LHCA1 protein, Arabidopsis; C493777:Lhca5 protein, Arabidopsis; D045342:Light-Harvesting Protein Complexes; D045331:Photosystem I Protein Complex; D010860:Pigments, Biological; D002734:Chlorophyll; D002338:Carotenoids