Thioredoxin activity in the C terminus of Phalaris S protein.
Self-incompatibility in the grass Phalaris coerulescens is controlled by two genes S and Z. Isolation and sequencing of two S alleles showed that they encode proteins that are highly conserved at the C terminus with significant homology to thioredoxin H proteins. In particular, the residues in and around the active site of thioredoxin, Trp-Cys-Gly-Pro-Cys, are perfectly conserved. The C terminus of the S protein has been expressed in Eschericia coli and purified to homogeneity on Ni-NTA resin. Functional assays showed that the protein has thioredoxin activity; it can act as a substrate for E. coli thioredoxin reductase and also catalyse the reduction of insulin by dithiothreitol. The possible role of thioredoxin-like activity of the S protein in mediating the incompatibility reaction in Phalaris is discussed.
Li
X
X
Centre for Cereal Biotechnology, Waite Institute, University of Adelaide, South Australia.
Nield
J
J
Hayman
D
D
Langridge
P
P
D000595:Amino Acid Sequence; D003001:Cloning, Molecular; D004220:Disulfides / Q000378:metabolism; D004926:Escherichia coli / Q000201:enzymology; D007328:Insulin / Q000378:metabolism; D008969:Molecular Sequence Data; D010084:Oxidation-Reduction; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D010957:Plasmids; D006109:Poaceae / Q000737:chemistry / Q000235:genetics*; D017386:Sequence Homology, Amino Acid; D013880:Thioredoxin-Disulfide Reductase / Q000378:metabolism; D013879:Thioredoxins / Q000378:metabolism*
D004220:Disulfides; D007328:Insulin; D010940:Plant Proteins; D013879:Thioredoxins; D013880:Thioredoxin-Disulfide Reductase