| Abstract: |
The central dogma of molecular biology defines the major avenue for the transfer of genetic information encoded in linear genomic DNA to three-dimensional effectors of function and structure, the proteins. Until recently, it has been hypothesized that this transfer of information required only two types of machinery, one to transcribe a DNA template into an RNA message, and a second to translate RNA into protein. It has been postulated that newly translated polypeptide chains contain sufficient information in their primary amino acid sequences to direct spontaneous folding into active tertiary structures. Recent experiments, however, indicate that in the intact cell both newly synthesized proteins and proteins translocated through several biological membranes do not in general fold spontaneously but rather utilize a third type of machinery, a folding machinery, to reach biologically active conformations. The best-studied class of components catalyzing such folding is the so-called chaperonins, groEL, hsp60, and RUBISCO binding protein, found, respectively, in the eubacterial cytoplasm and inside the evolutionarily related organelles, mitochondria and chloroplasts. At the level of primary structure, these three components share nearly 60% of their amino acids. At the level of quaternary structure, each is a homo-oligomeric complex composed of two stacked rings each containing seven radially arranged members. The functions of groEL and hsp60 have been shown to be essential for cell viability. © 1992, Elsevier B.V. |
