Molecular cloning and functional expression of a water-soluble chlorophyll protein, a putative carrier of chlorophyll molecules in cauliflower.
A cDNA for a water-soluble chlorophyll (Chl) protein (WSCP) from cauliflower (Brassica oleracea L. var botrys) was cloned and sequenced. The cDNA contained an open reading frame encoding 19 residues for a signal peptide and 199 residues for the mature form of WSCP. The sequence showed extensive homology to drought-stress-related, 22-kDa proteins in some Brassicaceae plants. Functional WSCP was expressed in Escherichia coli as a fusion protein with a maltose-binding protein (MBP). When the recombinant MBP-WSCP was incubated with thylakoid membranes, the MBP-WSCP removed Chls from these membranes. During this process, the monomer of the apo-MBP-WSCP successfully bound Chls and was converted into tetrameric holo-MBP-WSCP. The reconstituted MBP-WSCP exhibited absorption and fluorescent spectra identical to those of the native WSCP purified from cauliflower leaves. The Chl a/b ratio in native WSCP indicates a high content of Chl a, which was mainly due to the higher affinity of MBP-WSCP for Chl a. WSCP is the first example of a hydrophilic protein that can transfer Chls from thylakoid hydrophobic proteins. Possible functions of WSCP are discussed.
Satoh
H
H
Department of Biomolecular Science, Toho University, 2-2-1 Miyama, Funabashi, Chiba 274-8510, Japan. hsatoh@biomol.sci.toho-u.ac.jp
Nakayama
K
K
Okada
M
M
D000595:Amino Acid Sequence; D001483:Base Sequence; D001692:Biological Transport; D001937:Brassica / Q000378:metabolism*; D002734:Chlorophyll / Q000378:metabolism*; D003001:Cloning, Molecular; D018744:DNA, Plant / Q000737:chemistry; D045342:Light-Harvesting Protein Complexes; D008969:Molecular Sequence Data; D045322:Photosynthetic Reaction Center Complex Proteins / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism; D010940:Plant Proteins; D016415:Sequence Alignment; D012995:Solubility; D013050:Spectrometry, Fluorescence; D013054:Spectrophotometry, Atomic; D014867:Water
D018744:DNA, Plant; D045342:Light-Harvesting Protein Complexes; D045322:Photosynthetic Reaction Center Complex Proteins; D010940:Plant Proteins; C115715:WSCP protein, Brassica oleracea; D014867:Water; D002734:Chlorophyll