A small novel chloroplast ribosomal protein (S31) that has no apparent counterpart in the E. coli ribosome

Higher plant chloroplast ribosomes contain several novel protein components whose homologues are not present in the eubacterial E. coli ribosome, indicating a complex evolution of the chloroplast translational apparatus following the endosymbiotic event. Here we describe the isolation and characterization of a new small protein from spinach chloroplast ribosome which has, based on the amino acid sequence and immunological data, no counterpart in the E. coli ribosome. We suggest a nomenclature suitable for this protein and other novel proteins in the chloroplast ribosome.