Structural Studies on Prokaryotic Ribosomal Proteins

Until relatively recently, it was generally accepted that the functional components of the ribosome were the proteins and that the RNA component provided the rigid scaffold for maintaining their correct functional locations and orientations. Consequently, much early research was directed towards determining the locations, functions and structures of the individual ribosomal proteins (Wittmann, 1982). However, with the discovery that isolated RNA can manifest enzymic properties (Cech et al., 1981), the focus has shifted away from the proteins to the ribosomal RNA, and it is now generally accepted that the original roles for these components should be reversed. The highly conserved nature of ribosomal RNA (Noller, 1991) and the recent demonstration that 23S ribosomal RNA stripped of proteins still retains some peptidyl transferase activity (Noller et al., 1992) appear to support this notion. The ribosome is now regarded as an RNA-based organelle which has an absolute requirement for precisely folded RNA molecules in order to function correctly. The proteins’ principal role appears to be that of directing the ribosomal RNA molecules to these correctly folded structures during the assembly process, and perhaps modulating these structures during protein synthesis.