Posttranslational modifications of the beta subunit of a cryptomonad phycoerythrin. Sites of bilin attachment and asparagine methylation.
Determination of the partial amino acid sequence of the beta subunit of cryptomonad strain CBD phycoerythrin 566 established the nature, locations, and modes of attachment of the three bilin prosthetic groups and revealed a site of posttranslational methylation. Isolation of peptides cross-linked by a phycobiliviolin led to an unambiguous assignment of two thioether linkages, from residues beta-Cys-50 and beta-Cys-61 to this bilin. Two bilins were attached through single thioether linkages, a phycobiliviolin at beta-Cys-158 and a phycoerythrobilin at beta-Cys-82 (the residue numbering is that for B-phycoerythrin; Sidler, W., Kumpf, B., Suter, F., Morisset, W., Wehrmeyer, W., and Zuber, H. (1985) Biol. Chem. Hoppe-Seyler 366, 233-244). The partial sequences (99 residues) established for phycoerythrin 566 beta subunit showed a 79% identity with that of the red algal Porphyridium cruentum B-phycoerythrin beta subunit. A particularly remarkable finding is that the unique methylasparagine residue at position beta-72, highly conserved in cyanobacterial and red algal phycobiliproteins (Klotz, A. V., and Glazer, A. N. (1987) J. Biol. Chem. 262, 17350-17355), is also present at beta-72 in the cryptomonad phycoerythrin. Comparison of the locations of donor and acceptor bilins in cryptomonad phycoerythrin with those found for cyanobacterial and red algal phycobiliproteins showed different favored pathways of energy migration in the cryptomonad protein.
Wilbanks
S M
SM
Division of Biochemistry and Molecular Biology, University of California, Berkeley 94720.
Wedemayer
G J
GJ
Glazer
A N
AN
D000595:Amino Acid Sequence; D001216:Asparagine; D001654:Bile Pigments / Q000378:metabolism*; D001665:Binding Sites; D002850:Chromatography, Gel; D002851:Chromatography, High Pressure Liquid; D056890:Eukaryota / Q000378:metabolism*; D046911:Macromolecular Substances; D008745:Methylation; D008969:Molecular Sequence Data; D010799:Phycoerythrin / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism; D010860:Pigments, Biological / Q000235:genetics*; D011485:Protein Binding; D011499:Protein Processing, Post-Translational; D012689:Sequence Homology, Nucleic Acid; D013053:Spectrophotometry
D001654:Bile Pigments; D046911:Macromolecular Substances; D010860:Pigments, Biological; D010799:Phycoerythrin; D001216:Asparagine