Immunological evidence for the presence of the D1 and D2 proteins in PS II cores of higher plants

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Abstract
The psb A and psb D genes isolated from Poa annua and Triticum aestivum, respectively, have been expressed in Escherichia coli as β‐galactosidase fusion proteins and used to raise antibodies. The antibodies to the psb D gene product cross‐reacted with a lysine containing polypeptide with an apparent molecular mass of 31 kDa which was present in a PS II core preparation. In contrast, the antibody to thepsb A gene product recognised predominantly, a 34 kDa protein in the PS II core which was insensitive to treatments with a lysine specific protease. It is concluded that the latter polypeptide is the lysine‐free D1 protein and that the antibody raised to the psb D gene product monospecifically reacted with a component presumed to be the D2 protein. It is therefore suggested that the product of the psb D gene, as well as that of the psb A gene, is a component of the PS2 core complex of higher plants.