The structure of plastocyanin from the ­cyanobacterium Phormidium laminosum

• Published in: Acta crystallographica. Section D, Biological crystallography. Biological crystallography., 1999-02, Vol.55 (2), p.414-421
• Main Authors: Bond, Charles S., Bendall, Derek S., Freeman, Hans C., Guss, J. Mitchell, Howe, Christopher J., Wagner, Michael J., Wilce, Matthew C. J.
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Crystallography, X-Ray; Cyanobacteria - chemistry; Magnetic Resonance Spectroscopy; Molecular Sequence Data; plastocyanin (P. laminosum); Plastocyanin - chemistry; Protein Conformation; Sequence Homology, Amino Acid; Zinc - chemistry
• ISSN: 1399-0047; 0907-4449; 1399-0047
• DOI: 10.1107/S0907444998012074

The crystal structure of the `blue' copper protein plastocyanin from the cyanobacterium Phormidium laminosum has been solved and refined using 2.8 Å X‐­ray data. P. laminosum plastocyanin crystallizes in space group P43212 with unit‐cell dimensions a = 86.57, c = 91.47 Å and with three protein molecules per asymmetric unit. The final residual R is 19.9%. The structure was solved using molecular replacement with a search model based on the crystal structure of a close homologue, Anabaena variabilis plastocyanin (66% sequence identity). The molecule of P. laminosum plastocyanin has 105 amino‐acid residues. The single Cu atom is coordinated by the same residues – two histidines, a cysteine and a methionine – as in other plastocyanins. In the crystal structure, the three molecules of the asymmetric unit are related by a non‐crystallographic threefold axis. A Zn atom lies between each pair of neighbouring molecules in this ensemble, being coordinated by a surface histidine residue of one molecule and by two aspartates of the other.