Heterogeneity of the covalent structure of the blue copper protein umecyanin from horseradish roots

Abstract

The covalent structure of umecyanin has been determined by a combination of classical Edman degradation sequence analysis and plasma desorption, laser desorption, and electrospray ionization mass spectrometry. The preparation appeared to contain two isoforms having either a valine (75%) or an isoleucine (25%) residue at position 48. The polypeptide chain of 115 amino acids is strongly heterogeneous at its C-terminal end as a result of proteolytic cleavages at several places within the last 10 residues. The major fraction of the umecyanin preparation is only 106 residues long. The C-terminal tail 107-115 contains mainly alanine and glycine residues and a single hydroxyproline residue. In the native protein there is a disulfide bridge between Cys 91 and Cys 57, but in the apoprotein there is a disulfide shift that involves Cys 91 and one of the four copper binding residues (Cys 85). The three other ligand binding residues are His 44, His 90, and Gln 95. This tetrad of amino acids is the same as occurs in other type 1 copper proteins from plants such as cucumber peeling cupredoxin and lacquer tree stellacyanin. The umecyanin isoforms are glycoproteins with a glycan core having the same carbohydrate composition as that of horseradish peroxidase, a fact that is convincingly supported thanks to the high accuracy of the electrospray mass spectrometric technique. We suggest that the glycan may play a role in the association of the protein to the cellular membrane, but the precise functional role of umecyanin remains to be determined. We also discuss the evolutionary position of umecyanin in relation to the type 1 copper proteins in general.

Cotton BCP genes encoding putative blue copper‐binding proteins are functionally expressed in fiber development and involved in response to high‐salinity and heavy metal stresses

“…Domain III, existed in many GhBCPs, was rich in Pro, Ser and Thr, and was highly variable in length, sequence and composition. It is likely that certain of the Pro in these domains will be hydroxylated during protein maturation, as indeed is the case for cucumber peeling cupredoxin (CPC) and umecyanin (Mann et al 1992, van Driessche et al 1995).…”

A phytocyanin-related early nodulin-like gene, BcBCP1, cloned from Boea crassifolia enhances osmotic tolerance in transgenic tobacco

“…Horseradish umecyanin, one kind of phytocyanin from root, was isolated bound to peroxidase. It was suggested to function together with peroxidase in the root cell membrane region (Vandriessche et al, 1995). The pea (P. sativum) blue copper binding protein was reported to be correlated with lignin deposition in pod endocarp (Drew and Gatehouse, 1994).…”

Genome-wide identification, classification, and expression analysis of the phytocyanin gene family in Phalaenopsis equestris

“…* Corresponding author: fax: (+86)01062888687, e-mail: lilubin@126.com UCs are chimeric glycoproteins, whereas PLCs are not (Nersissian et al 1998). Similarly, SCs have both a copper-binding domain (two His, one Cys, and one Gln) and a glycoprotein-like domain (Mann et al 1992, Van Driessche et al 1995. SCs and UCs contain N-linked glycosylation sites through an asparagine (Asn) residue, as well as O-linked glycosylation sites through serine (Ser) and hydroxyproline (Hyp) residues.…”