UCLACYANINS, STELLACYANINS, AND PLANTACYANINS APE DISTINCT SUBFAMILIES OF PHYTOCYANINS - PLANT-SPECIFIC MONONUCLEAR BLUE COPPER PROTEINS

Citation
Am. Nersissian et al., UCLACYANINS, STELLACYANINS, AND PLANTACYANINS APE DISTINCT SUBFAMILIES OF PHYTOCYANINS - PLANT-SPECIFIC MONONUCLEAR BLUE COPPER PROTEINS, Protein science, 7(9), 1998, pp. 1915-1929
Citations number
74
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Biology
Journal title
ISSN journal
0961-8368
Volume
7
Issue
9
Year of publication
1998
Pages
1915 - 1929
Database
ISI
SICI code
0961-8368(1998)7:9<1915:USAPAD>2.0.ZU;2-2
Abstract
The cDNAs encoding plantacyanin from spinach were isolated and charact erized. In addition, four new cDNA sequences from Arabidopsis ESTs wer e identified that encode polypeptides resembling phytocyanins, plant-s pecific proteins constituting a distinct family of mononuclear blue co pper proteins. One of them encodes plantacyanin from Arabidopsis, whil e three others, designated as uclacyanin 1, 2, and 3, encode protein p recursors that are closely related to precursors of stellacyanins and a blue copper protein from pea pods. Comparative analyses with known p hytocyanins allow further classification of these proteins into three distinct subfamilies designated as uclacyanins, stellacyanins, and pla ntacyanins. This specification is based on (1) their spectroscopic pro perties, (2) their glycosylation state, (3) the domain organization of their precursors, and (4) their copper-binding amino acids. The recom binant copper binding domain of Arabidopsis uclacyanin 1 was expressed , purified, and shown to bind a copper atom in a fashion known as ''bl ue'' or type 1. The mutant of cucumber stellacyanin in which the gluta mine axial ligand was substituted by a methionine (Q99M) was purified and shown to possess spectroscopic properties similar to uclacyanin I rather than to plantacyanins. Its redox potential was determined by cy clic voltammetry to be +420 mV, a value that is significantly higher t han that determined for the wild-type protein (+260 mV). The available structural data suggest that stellacyanins land possibly other phytoc yanins) might not be diffusible electron-transfer proteins participati ng in long-range electron-transfer processes. Conceivably, they are in volved in redox reactions occurring during primary defense responses i n plants and/or in lignin formation.