GAMMA-PUROTHIONINS - AMINO-ACID-SEQUENCE OF 2 POLYPEPTIDES OF A NEW FAMILY OF THIONINS FROM WHEAT ENDOSPERM

Two homologous sulfur-rich basic polypeptides form wheat endosperm, so-called γ1-purothionin and γ2-purothionin, are described. Purification involves extraction with volatile solvents and ammonium bicarbonate fractionation followed by reversed-phase high-performance liquid chromatography. The complete primary structure of these two polypeptides has been determined by automatic degradation of the intact, S-carboxymethylated γ-purothionins and peptides obtained by enzymatic cleavage. γ1-Purothionin and γ2-purothionin consist of 47 amino acids with an assessed molecular weight of 5239 and 5151 Da, respectively and 8 cysteines organized in 4 disulfide bridges. They present a high degree of homology among themselves (89% of identity) and are the first two thionin-like polypeptides, so-called y-thionins, described from wheat endosperm. © 1990.