title: Isolation and localization of N4-methylasparagine in phycobiliproteins from the cyanobacterium Mastigocladus laminosus.
abstract: The occurrence of post-translationally methylated asparagine residues in beta AP from Anabaena variabilis, Synechococcus PCC 6301 and Porphyridium cruentum has recently been reported (Klotz, A.V., Leary, J.A. & Glazer, A.N. (1986) J. Biol. Chem. 261, 15891-15894). We reinvestigated the amino-acid compositions of all phycobiliproteins from Mastigocladus laminosus. During total hydrolysis of beta AP, beta 16.2 and beta PC one mol methylamine per mol protein was released. These proteins were chemically and enzymatically fragmented and the sequences of the fragments containing the modified asparagine residue were determined by automated Edman degradation. Residues beta AP72, beta 16.2 72 and beta PC 72 were identified as N4-methylasparagine. This derivative of asparagine was also found at a homologous position in beta PE of Calothrix. In the x-ray structure model of C-phycocyanin (PC) the residue beta PC 72 points towards the chromophore beta 84, presumably having an effect on the spectroscopic characteristics of this light harvesting pigment protein complex.
mesh_terms: D000595:Amino Acid Sequence; D001216:Asparagine / Q000031:analogs & derivatives* / Q000032:analysis; D000458:Cyanobacteria / Q000032:analysis*; D007202:Indicators and Reagents; D045342:Light-Harvesting Protein Complexes; D008969:Molecular Sequence Data; D010940:Plant Proteins / Q000032:analysis*; D011487:Protein Conformation
chemical_list: D007202:Indicators and Reagents; D045342:Light-Harvesting Protein Complexes; D010940:Plant Proteins; C054431:gamma-N-methylasparagine; D001216:Asparagine