Abstract
An open reading frame with significant similarity to the secY gene of Escherichia coli has been found within a ribosomal protein operon on the plastid genome of the chlorophyll c‐containing alga Cryptomonas Φ. The gene encodes a protein or 420 amino acids (molecular weight 46.906 daltons) and contains ten potential membrane‐spanning domains, as in the E. coli homologue. This report of a secY homologue in a plastid genome provides preliminary evidence that a prokaryotic‐like protein export system may be operating in plastids.