Molecular characterization of the terminal energy acceptor of cyanobacterial phycobilisomes

• Published in: Proceedings of the National Academy of Sciences - PNAS 1990-03, Vol.87 (6), p.2152-2156
• Main Authors: Houmard, J. (Institut Pasteur, Paris, France), Capuano, V, Colombano, M.V, Coursin, T, Tandeau de Marsac, N
• Format: Article
• Language: English
• Subjects: ACIDE AMINE; ADN; ALGAE; ALGUE; Amino Acid Sequence; AMINO ACIDS; AMINOACIDOS; Base Sequence; BIOLOGIA MOLECULAR; BIOLOGIE MOLECULAIRE; CALOTHRIX; Chromophores; CODE GENETIQUE; CODIGO GENETICO; Cyanobacteria; Cyanobacteria - genetics; CYANOPHYTA; Cylinders; DNA; energy transduction; fremyella diplosiphon; GENE; Gene Library; GENES; GENETIC CODE; Light-Harvesting Protein Complexes; Macromolecular Substances; MOLECULAR BIOLOGY; Molecular Sequence Data; NUCLEOTIDE; NUCLEOTIDES; NUCLEOTIDOS; Operator regions; Operon; Operons; PEPTIDE; PEPTIDES; PEPTIDOS; photosynthesis; phycobiliproteins; Phycobilisome; Phycobilisomes; Pigments, Biological - metabolism; Plant Proteins - genetics; Plant Proteins - metabolism; Plasmids; POLYPEPTIDES; Protein Conformation; PROTEINAS; PROTEINE; PROTEINS; Restriction Mapping; secondary structure; Sequence Homology, Nucleic Acid
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.87.6.2152

Cyanobacteria harvest light energy through multimolecular structures, the phycobilisomes, regularly arrayed at the surface of the photosynthetic membranes. Phycobilisomes consist of a central core from which rods radiate. A large polypeptide (LCM, 75-120 kDa) is postulated to act both as terminal energy acceptor and as a linker polypeptide that stabilizes the phycobilisome architecture. We report here the characterization of the gene (apcE) that encodes this LCMpolypeptide in Calothrix sp. PCC 7601. It is located upstream from the genes encoding the major components of the phycobilisome core (allophycocyanin) and is part of the same operon. The deduced amino acid sequence shows that the N-terminal region of LCMshares homology with the other phycobiliprotein subunits and thus constitutes the chromoprotein domain. The other part of the molecule is made up of four repeated domains that are highly homologous to the N-terminal regions of the phycocyanin rod linker polypeptides. The predicted secondary structure of the different domains of the LCMis discussed in relation to the different roles and properties of this large molecule.