Examination of protein sequence homologies: I. Eleven Escherichia coli L7/L12-type ribosomal "A" protein sequences from eubacteria and chloroplast.

Seven complete and four partial sequences of Escherichia coli L7/L12-type ribosomal "A" proteins obtained from various bacteria (E. coli, Bacillus subtilis, Micrococcus lysodeikticus, Rhodopseudomonas spheroides, Desulfovibrio vulgaris, Streptomyces griseus, Bacillus stearothermophilus, Clostridium pasteurianum, Arthrobacter glacialis, and Vibrio costicola) and spinach chloroplast have been reexamined using a computer program that searches for homologous tertiary structures. Comparison matrices for the sequences show that they match the sequence of E. coli L7 (EL7) if one assumes the insertion or deletion of certain residues at sites corresponding to residues 1, 38, 49, and 92 of EL7. That two additional insertion points are found only in the spinach chloroplast protein suggests that the chloroplast protein probably diverged from the bacterial forms. Further phylogenetic relationships among these 11 prokaryote-type "A" proteins are discussed with respect to average correlation coefficients computed, taking into account the existence of the gaps.