The nature of the subunit-subunit interaction in E. coli 70S ribosomes will be studied, and the structural effects and functional roles of the various factors influencing this interaction will be investigated with particular focus on 3' end of the rRNAs. The topology of the E. coli ribosome will be investigated using a strain deficient in an RNase involved in processing the 5' end of precursor 16S rRNA. The ribosomal proteins in the neighborhood of the 5' end of 16S rRNA will be determined. Structural features of the yeast ribosome will be studied and factors which have functional roles in the initiation of protein synthesis will be isolated.