Phytocyanins structure

The molecular structure of another blue protein, the phytocyanin (phytocyanins are electron carriers found in the non-photosynthetic part of plants) cucumber basic protein (FW=10 100), also known as plantacyanin, is shown in Figure 33.60... 

The first class is cupredoxins—single-domain blue copper proteins composed of only one BCB domain. These proteins include plastocyanin, azurin, pseudoazurin, amicyanin, auracyanins, rusticyanin, halocyanin, and sulfocyanin (see Section IV). Plantacyanin of the phytocyanin family (Section V), subunit II of the cytochrome c oxidase, and the recently characterized nitrosocyanin also fall into this class. The last two are single BCB domain polypeptides closely related structurally to cupredoxins, but harboring, respectively, a binuclear copper site known as CuA and a novel type of copper-binding site called red (see Sections IX and X). 

Crystal structures of three phytocyanins are currently available. Two are for plantacyanins, from cucumber (also known as cucumber basic protein) (Guss et al., 1988, 1996) and from spinach (Einsle et al., 2000), and one is for the recombinant BCB domain of cucumber stella-cyanin (Hart et al., 1996). The three proteins display folding topology identical to one another, suggesting that phytocyanins fold into a uniform structure, which can be designated as a phytocyanin fold. As a historical note, the crystallization of the cucumber basic protein and its preliminary crystallographic data were reported in 1977, before any structure of a blue copper protein was available (Colman et al., 1977). However, the structure was solved in 1988 only by application of the then newly... 

With the exception of the plantacyanins, phytocyanins are chimeric proteins in their mature forms. They are composed of two structurally distinct sequence motifs, a 100-109-amino acid blue copper domain followed by a domain that varies in length between 30-220 amino acids, lacks any obvious consensus sequence, but resembles heavily glycosylated arabinogalactan proteins (AGP). Where such AGP domains are present, they are followed by a hydrophobic sequence predicted to provide a signal for the attachment of a GPI moiety, which anchors the protein to the cell surface (Figure 2). This cell-surface attachment of phytocyanins... 

At this writing, the three-dimensional sttuctures of eight different naturally occurring type 1 copper proteins are known. These include the cupredoxins plastocyanin at 1.33 A resolution (pdb code 1 PTC), azurin at 1.8 A (pdb code 2AZA), pseudoazurin at 1.55 A (pdb code IPAZ), amicyanin at 1.3 A (pdb code lAAC), auracyanin at 1.55 A (pdb code IQHQ), rusticyanin at 1.9 A (pdb code IRCY), and the phytocyanins cucumber basic protein at 1.8 A (pdb code2CBP), and stellacyanin at 1.6 A (pdb code IJER) Atomic coordinates for these and all other single-domain type 1 copper proteins are available from the Research Collaboratory for Structural Bioinformatics (RCSB) Protein Data Bank (PDB) and can be accessed online at www.rcsb.org/pdb/. 

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