Studies of the Amino Acid Sequence of Plastocyanin from Rumex obtusifolius (Broad-Leaved Dock)

Plastocyanins are low-molecular-weight cuproproteins, which occur in the chloroplasts of plants and algae. The exact biological function of the protein remains uncertain, but is probably associated with photosynthetic electron transport (Gregory, 1971). The small size and blue colour of the protein simplify the purification of plastocyanin, and studies with a number of species have been reported (Kelly & Ambler, 1973; Ramshaw et al., 1973). The amino acid sequences of the molecule from Chlorella fusca (Kelly & Ambler, 1973) and Solanum tuberosum (Ramshaw et al., 1974) have been reported. The aim of the present investigation was to determine the amino acid sequence of the protein from dock as part of aprogrammefor theelucidation of phylogeneticrelationships in plants (Boulter et al., 1972). Plastocyanin was isolated from dock leaves by the procedures described previously (Ramshaw et al., 1973). About 40mg of purified material was finally available for sequen-