The complete amino acid sequence of R‐phycocyanin‐I α and β subunits from the red alga Porphyridium cruentum

Abstract

We present here the complete primary structure of R-phycocyanin-I a and p subunits from the red alga Porphyridium cruentum. The a chain is composed of 162 amino acid residues (18049Da, calculated from sequence, including chromophore) and carries a phycocyanobilin pigment covalently linked to Cys84. The p chain contains 172 amino acids (19344Da, calculated from sequence, including chromophores) and carries a phycocyanobilin pigment covalently linked at Cys82 and a phycoerythrobilin pigment at Cys153. A y-N-methyl asparagine residue was also characterised at position ,872 similar to other phycobiliprotein , 6 subunits. R-phycocyanin-I from Porphyridium cruentum shares high sequence identity with C-phycocyanins (69 -83%), R-phycocyanins (66-70%) and in a less extent with phycoerythrocyanins (57-65%) from various sources.The presented phylogenetic trees are based on a comparison of all phycobiliprotein amino acid sequences known so far and confirm the clear affiliation of the R-phycocyanins in the phycocyanin family. In spite of their particular phycobilin pattern, they do not represent intermediate forms between the phycocyanin and the phycoerythrin family. Phycoerythrocyanin, a phycocyanin-related phycobiliprotein adapted to green light harvesting, is also shown to belong to the phycocyanin family. However, the phycoerythrocyanins diverge from phycocyanins in their different function and it is suggested that they should be assigned to a separate group within the phycocyanin family.Phycobilisomes represent the main accessory light-harvesting antenna of cyanobacteria and red algae (Cohen-Bazire and Bryant, 1982;Zuber, 1983Glazer, 1984Glazer, , 1985Gantt, 1988;Bryant, 1991; Sidler, 1994). Their major components, the phycobiliproteins, are constituted of a and p subunits (16-18 kDa and 18-20 kDa respectively) carrying one, two or three open-chain tetrapyrroles (bilins) per subunit as prosthetic groups. Both subunits are aggregated in vivo to heterotrimers (an3 or hexamers (anb. Electron microscopy and crystal structure analysis show that the trimer complex is the basic building block of the phycobilisome (Schirmer et al., 1985). The ap monomer aggregates in a disc-shaped complex with a diameter of 11 nm and a length of 3 nm. A hexamer is built up of two trimers stacked face-to-face (Schirmer et al., 1986). The formation of higher aggregatesCorrespondence to H.

Isolation, Characterization and Electron Microscopy Analysis of A Hemidiscoidal Phycobilisome Type from the Cyanobacterium Anabaena sp. PCC 7120

“…Ducret (Dissertation ETH no. 10731, 1994). 1989; Grossman, 1990;MacColl and Guard-Friar, 1987;Morschel and Rhiel, 1987;Sidler, 1994;Tandeau de Marsac, 1991;Wehrmeyer, 1990;Zuber, 1985Zuber, ,1986Zuber et al, 1987). The most common and best described phycobilisorne belongs to the hemidiscoidal type, which is typically isolated in cyanobacteria.…”

“…Hexameric complexes are formed by the aggregation of two trimeric units into a head-to-head configuration (Schirmer et al, 1986 ;Ficner et al, 1992) exhibiting a dimension of 11 nmX 6 nm. Phycobiliproteins may be divided into three main groups by comparing their chromophore compositions, their immunological properties and their amino acid sequences (Zuber, 1985(Zuber, , 1986Glazer, 1987;McColl and Guard-Friar, 1987;Ducret et al, 1994;Sidler, 1994): the phycoerythrins (A,,, = 490-570 nm); the phycocyanins and phycoerythrocyanins (A, , , = 490-625 nm and 560-600 nm, respectively) ; and the allophycocyanins (A, , , = 650-665 nm). Each phycobiliprotein type fulfills a specific function in the phycobilisome as reflected in its distribution in the antenna (Fig.…”

“…About 10-15% of the protein content of the phycobilisome is accounted for by colorless proteins, the linker polypeptides. They represent the skeleton of the antennae as they promote the specific aggregation of the phycobiliproteins to the highly organized phycobilisome structure (for reviews, see Bryant, 1991 ;Gantt, 1988;Glazer, 1987;Sidler, 1994;Tandeau de Marsac, 1991). Linker polypeptides have been divided into three categories on the basis of their molecular masses.…”

Biosynthesis of Cyanobacterial Phycobiliproteins in Escherichia coli : Chromophorylation Efficiency and Specificity of All Bilin Lyases from Synechococcus sp. Strain PCC 7002

“…The methyltransferase reaction pro-duces a highly conserved ␥-N-methylasparagine residue at the ␤-72 position of almost all ␤-subunits isolated from cyanobacteria, red algae, and cryptomonads (17,35,36,45,65). This modification is thought to change the environment of the chromophore at position ␤-82 to minimize the rates of nonradiative energy loss within PBS (59,60).…”

Biogenesis of Phycobiliproteins

“…The presence of the unusual post-translational modification, ␥-N-methylasparagine, at the Asn 72 residue of PBP ␤-subunits in most cyanobacteria, red algae, and cryptomonads has been well documented (2,3,7,8). Klotz and Glazer (3) examined a range of cyanobacterial PBP for the release of methylamine after acid hydrolysis and found that PBP ␤-subunits were only rarely unmethylated.…”