We are studying various aspects of bacteriophage Q Beta RNA replication. The enzyme responsible for this process contains one phage-coded and three host-coded polypeptides. These latter polypeptides all function in protein biosynthesis in the uninfected host. We are studying the question of whether the structures and functions of these host polypeptides important in one biosynthetic process ar also important in the other. We are also investigating the mechanism by which Q Beta RNA replicase can preferentially recognize and initiate RNA synthesis on Q Beta RNA. We have developed a technique for measuring specific interactions between ligands and particular subunits of multi-subunit proteins. We have used this technique to elucidate interactions between a variety of proteins (Q Beta replicase, RNA polymerase, protein synthesis elongation factors) and molecules with which they interact.