Functional role of Chaperonin protein complexes

The chaperonins are high-molecular weight protein complexes present in all living cells; they are thought to participate in the folding or refolding of cellular proteins and may also have a function in RNA metabolism. Recently, it has been reported that the chaperonin of thermophilic archeon Sulfolobus solfataricus interacts with the 16S ribosomal RNA and participates in the early stages of its maturation. By means of contrast variation SANS we demonstrate that the native S. solfataricus chaperonin is complexed with a nucleic acid molecule of about 1600 nucleotides, which becomes detached from the protein mojety in the presence of ATP. Treatment with ATP also provokes a conformational change in the protein complex, compacting its structure and closing its central hole. The result lends support to the hypothesis that Sulfolobus chaperonin participates in ribosomal RNA maturation and ribosome assembly. (C) 2000 Elsevier Science B.V. All rights reserved.