Volume 98, Numbers 1-3, 479-488, DOI: 10.1007/s11120-008-9368-0

The small CAB-like proteins of Synechocystis sp. PCC 6803 bind chlorophyll
In vitro pigment reconstitution studies on one-helix light-harvesting-like proteins

Patrik Storm, Miguel A. Hernandez-Prieto, Laura L. Eggink, J. Kenneth Hoober and Christiane Funk

From the issue entitled "Recent Perspectives of Photosystem II: Structure, Function and Dynamics - In honor of Kimiyuki Satoh and Thomas Wydrzynski"

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Abstract

The large family of light-harvesting-like proteins contains members with one to four membrane spanning helices with significant homology to the chlorophyll a/b-binding antenna proteins of plants. From structural as well as evolutionary perspective, it is likely that the members of this family bind chlorophylls and carotenoids. However, undisputable evidence is still lacking. The cyanobacterial small CAB-like proteins (SCPs) are one-helix proteins with compelling similarity to the first and third transmembrane helix of LHCII (LHCIIb) including the chlorophyll-binding motifs. They have been proposed to act as chlorophyll-carrier proteins. Here, we analyze the in vivo absorption spectra of single scp deletion mutants in Synechocystis sp. PCC 6803 and compare the in vitro pigment binding ability of the SCP pairs ScpC/D and ScpB/E with the one of LHCII and a synthetic peptide containing the chlorophyll-binding motif (Eggink LL, Hoober JK (2000) J Biol Chem 275:9087–9090). We demonstrate that deletion of scpB alters the pigmentation in the cyanobacterial cell. Furthermore, we are able to show that chlorophylls and carotenoids interact in vitro with the pairs of ScpC/D and ScpB/E, demonstrated by fluorescence resonance energy transfer and circular dichroism.

Keywords  Antenna - Chlorophyll-binding protein - Cyanobacteria - Early-light-induced proteins (ELIPs) - High-light-induced proteins (HLIPs) - Light-harvesting complex -  Synechocystis sp. PCC 6803

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