12/18/2023 0 Comments Do prokaryotes have chaperone proteins![]() ![]() Rather, chaperones catalyze protein folding by assisting the self-assembly process. It is important to note that chaperones do not convey additional information required for the folding of polypeptides into their correct three-dimensional conformations the folded conformation of a protein is determined solely by its amino acid sequence. Subsequent studies have extended the concept to include proteins that mediate a variety of other assembly processes, particularly protein folding. Chaperones thus act as catalysts that facilitate assembly without being part of the assembled complex. ![]() Nucleoplasmin binds to histones and mediates their assembly into nucleosomes, but nucleoplasmin itself is not incorporated into the final nucleosome structure. The term “ chaperone” was first used by Ron Laskey and his colleagues to describe a protein (nucleoplasmin) that is required for the assembly of nucleosomes from histones and DNA. Proteins that facilitate the folding of other proteins are called molecular chaperones. The proper folding of proteins within cells is mediated by the activities of other proteins. More recent studies, however, have shown that this is not an adequate description of protein folding within the cell. Protein folding thus appeared to be a self-assembly process that did not require additional cellular factors. This was initially established by Christian Anfinsen’s experiments demonstrating that denatured RNase can spontaneously refold in vitro to its active conformation (see Figure 2.17). ![]() The classic principle of protein folding is that all the information required for a protein to adopt the correct three-dimensional conformation is provided by its amino acid sequence. The three-dimensional conformations of proteins result from interactions between the side chains of their constituent amino acids, as reviewed in Chapter 2. ![]()
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