Poster: Photosynthesis

Abs # 337: Molecular cloning and functional expression of photoconvertible Water-soluble chlorophyll protein CP668 from Chenopodium album.

Presenter:	Yoshikawa, Mami , hsatoh@biomol.sci.toho-u.ac.jp
Authors	Yoshikawa, Mami  (A)   Satoh, Hiroyuki  (A)   Nakayama, Katsumi  (A)   Okada, Mitsumasa  (A)
Affiliations:	(A): Dept. of Biomol. Sci., Toho University

To date, two different types of water-soluble Chl protein (WSCP) have been identified; a Chenopodium-type, photoconvertible WSCP (Class I) and a Brassica-type, non-photoconvertible WSCP (Class II). Several studies focusing on Class II WSCPs have recently been conducted and have revealed that WSCPs exhibit sequence similarity with drought-stress induced proteins in the Brassicaceae family. In contrast to the Class II WSCPs, research on the Class I WSCPs has mainly focused on the physicochemical and biochemical aspects. CP668, a Class I WSCP purified from Chenopodium album, was the first WSCP to be documented and similar WSCPs have since been reported in species belonging to the Chenopodium, Atriplex, Polygonum, and Amaranthus genera. The most interesting property of CP668 is its conversion into a photoreaction product, CP743, upon illumination. An initial Chl a component with an absorption peak at 668 nm is converted into another pigment with a peak at 743 nm via a predicted transient Chl species in a triplet excited state. However, molecular biological characterization of this WSCP has not yet been attempted. In the present study, we cloned a cDNA encoding for CP668 from C. album. The cDNA contained an open reading frame encoding 27 residues for a signal peptide and 169 residues for the mature form of WSCP. The sequence did not exhibit homology with Class II WSCPs from Brassicaceae plants. From this cDNA, a functional WSCP was expressed in E. coli. Photoconversion activity was detected in the recombinant CP668. The molecular properties of this cDNA and its product will be presented.