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THE γ SUBUNITS OF PHYCOERYTHRIN FROM A RED ALGA: POSITION IN PHYCOBILISOMES AND SEQUENCE CHARACTERIZATION
Author(s) -
Apt Kirk E.,
Metzner Sandra,
Grossman Arthur R.
Publication year - 2001
Publication title -
journal of phycology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.85
H-Index - 127
eISSN - 1529-8817
pISSN - 0022-3646
DOI - 10.1046/j.1529-8817.2001.037001064.x
Subject(s) - phycobilisome , biology , protein subunit , peptide sequence , biochemistry , protein primary structure , phycoerythrin , complementary dna , amino acid , oligonucleotide , linker , microbiology and biotechnology , cyanobacteria , genetics , gene , flow cytometry , bacteria , computer science , operating system
Aglaothamnion neglectum Feldman‐Mazoyer has two γ subunits, γ 31 and γ 33 , that are associated with phycoerythrin in the light‐harvesting phycobilisomes. We demonstrate that these subunits are spatially separated within the phycobilisome, with the γ 31 subunit present at the distal end of phycobilisome rods and the γ 33 subunit present on the proximal end. These subunits are thought to link phycoerythrin hexamers together in the rod substructure, serving a role analogous to that of linker polypeptides of cyanobacteria (although unlike the cyanobacterial linker polypeptides they are chromophorylated). The sequencing of tryptic polypeptides of the γ subunits enabled us to prepare oligonucleotides encoding different regions of γ 31 . These oligonucleotides were used as primers to generate a probe for isolating a γ 31 cDNA clone. Characterization of the cDNA clone predicts a polypeptide of 280 amino acids with a 42 amino acid presequence that is characteristic of a transit peptide, the peptide that targets proteins to chloroplasts of vascular plants. The γ 31 subunit has 50% similarity to the previously characterized γ 33 subunit but has no identifiable similarity to functionally related polypeptides present in cyanobacterial phycobilisomes or to any other polypeptides in the databases. A repeat of 95 amino acids is present in the red algal γ subunit sequences, suggesting that these proteins were generated by a gene duplication followed by fusion of the duplicate sequences.