Seed proteins of the seagrass Zostera capricorni

Abstract

Proteins were extracted from the seeds of the seagrass Zostera capricorni Aschers. and analysed by polyacrylamide gel electrophoresis. Pore-gradient gel electrophoresis revealed a predominant storage protein of estimated M r 340 000, which we have termed ‘zosterin’. This protein accounted for about 80% of extractable protein. Dissociation of proteins by the anionic detergent, sodium dodecylsulphate (SDS), in the absence and presence of 2-mercaptoethanol confirmed that disulphide-linked subunits associate to form zosterin. On electrophoresis in uniform-pore gels set from 10% acrylamide, five major subunits were resolved (polypeptides I–V), of estimated M r 30 000, 27 500, 24 000, 22 000 and 20 500, respectively. These subunits associate to form disulphide-bridged constituents of two size classes, M r 54 000 and 46 000, with the former predominating (∼ 2:1). Zosterin is clearly a counterpart of legumin, one of the major storage proteins of legume seeds.