Published online by Cambridge University Press: 10 August 2009
Introduction
In the beginning, bacteria evolved chaperonins (Cpns) to help in the folding of other proteins. Then, about one and a half billion years ago, bacteria began to live with eukaryotic cells. The career of the chaperonin began to expand beyond the protein folding area, and they developed new functions in order to adapt to the eukaryotic evolutionary niche. As the eukaryotes became ever more complex, the chaperonins evolved into cell-cell signalling molecules. The sophistication of this new role has only recently begun to emerge.
The chaperonins that are the subject of this chapter belong to the 60- and 10-kDa classes and are called Cpn60 and Cpn10, respectively. The folding actions of these proteins have been described in detail in Chapter 1. If there is more than one Cpn60 or Cpn10 in any one species, they are called Cpn60.1, Cpn60.2 and so on [1]. Cpn60 proteins are also called heat shock protein (Hsp) 60 or 65, and Cpn10s are also named Hsp10. For example, the Mycobacterium tuberculosis genome contains two cpn60 genes. One of these, termed cpn60.1 [2], appears to form an operon with the cpn10 gene. This is the usual relationship in most bacteria. The second cpn60 gene encodes Cpn60.2, the well-known Hsp65 protein of M. tuberculosis, and is found elsewhere in the genome.
What is a cell-cell signalling molecule?
A cell-cell signalling molecule is one that directly communicates a message from one cell to another.
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