Uclacyanins, stellacyanins, and plantacyanins are distinct subfamilies of phytocyanins: Plant‐specific mononuclear blue copper proteins

Abstract

The cDNAs encoding plantacyanin from spinach were isolated and characterized. In addition, four new cDNA sequences from Arubidopsis ESTs were identified that encode polypeptides resembling phytocyanins, plant-specific proteins constituting a distinct family of mononuclear blue copper proteins. One of them encodes plantacyanin from Arubidopsis. while three others, designated as uclacyanin 1, 2, and 3, encode protein precursors that are closely related to precursors of stellacyanins and a blue copper protein from pea pods. Comparative analyses with known phytocyanins allow further classification of these proteins into three distinct subfamilies designated as uclacyanins, stellacyanins, and plantacyanins. This specification is based on (1) their spectroscopic properties, (2) their glycosylation state, (3) the domain organization of their precursors, and (4) their copper-binding amino acids. The recombinant copper binding domain of Arubidopsis uclacyanin I was expressed, purified, and shown to bind a copper atom in a fashion known as "blue" or type 1. The mutant of cucumber stellacyanin in which the glutamine 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 cyclic voltammetry to be +420 mV, a value that is significantly higher than that determined for the wild-type protein (+260 mV). The available structural data suggest that stellacyanins (and possibly other phytocyanins) might not be diffusible electron-transfer proteins participating in long-range electron-transfer processes. Conceivably, they are involved in redox reactions occurring during primary defense responses in plants and/or in lignin formation.

Novel and Mechanical Stress–Responsive MicroRNAs in Populus trichocarpa That Are Absent from Arabidopsis

“…A validated target for ptr-miR408, a plastocyanin-like protein, is interesting because this class of proteins is believed to mediate lignin polymerization (Nersissian et al, 1998). The near absence of ptr-miR408 transcripts in developing xylem, the major lignification tissue, and the moderate expression of ptr-miR408 in low lignin containing tissues, phloem and leaf (Figure 2), support the role of ptr-miR408 in coordinating lignin deposition in different tissues.…”

Genome-Wide Identification of Nodule-Specific Transcripts in the Model Legume Medicago truncatula

“…These include TCs that encode proteins similar to: (a) purine permease, a high-affinity transporter for adenine, cytosine, and purine derivatives (Gillissen et al, 2000); (b) plantacyanin, a plant-specific blue copper protein, apparently involved in the defense response (Nersissian et al, 1998); (c) a homolog of an Arabidopsis embryospecific protein, whose cellular function is yet to be understood; (d) B12D protein, a protein known to be accumulated in plants during embryo development, seed maturation, and leaf senescence (Aalen et al, 1994;Huang et al, 2001); (e) remorin, a membrane phosphoprotein, suggested to be involved in intercellular communications (Reymond et al, 1996); (f) 2-on-2 hemoglobin, the higher plant homolog of the "truncated" hemoglobins found in bacteria, protozoa, and algae, which possess unique biochemical properties that are likely distinct from those of other plant hemoglobins (Watts et al, 2001); and (g) calmodulinlike proteins.…”

“…The nucleotide sequence of TC32101 is 97% identical to that of nodulin MsNod202 encoding a plantacyanin from M. sativa . Together with two other nodulins, ENOD16 and ENOD20 (Greene et al, 1998), corresponding to nodule-specific TC40417 and TC28429, these proteins contain a copper-binding domain characteristic of a group of plant phytocyanins proposed to be involved in primary defense response (Nersissian et al, 1998). Another copper-related nodule-specific TC appears to encode a putative copper transporter (TC37150).…”

Cell wall proteins: a new insight through proteomics

“…Redox reactions play many roles in plant cell walls during development as well as in response to pathogen attacks [54][55][56][57]. In addition to peroxidases, several CWP might be involved in such processes.…”