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Alkaline transition of phytocyanins: A comparison of stellacyanin and umecyanin

Lookup NU author(s): Professor Christopher Dennison, Anne Lawler


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The effect of pH on Cu(I) and Cu(II) forms of the isolated soluble domain of the stellacyanin from Rhus vernicifera (SCu), the Japanese lacquer tree, has been studied by electronic and NMR spectroscopy and using direct electrochemical measurements. A pKa value of 10.1-10.4 is observed for the alkaline transition in this oxidized phytocyanin and results in a slightly altered active-site structure, as indicated by changes in the visible and paramagnetic 1H NMR spectra. Electrochemical studies show that the pKa value for this transition in SCu(I) (reduced SCu) is 11.0. These results are compared with those recently obtained for other phytocyanins, and in particular umecyanin. In all cases, the alkaline transition is caused by the deprotonation of the surface lysine residue adjacent to the axial ligand. This lysine residue is completely conserved in known phytocyanin sequences. Also highlighted in these studies are the remarkable active-site similarities between stellacyanin and umecyanin.

Publication metadata

Author(s): Dennison C, Harrison MD, Lawler AT

Publication type: Article

Publication status: Published

Journal: Biochemical Journal

Year: 2003

Volume: 371

Issue: 2

Pages: 377-383

ISSN (print): 0264-6021

ISSN (electronic): 1470-8728

Publisher: Portland Press Ltd.


DOI: 10.1042/BJ20021869

PubMed id: 12529171


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