Cell Biology

I Need My Space

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Science  30 May 2008:
Vol. 320, Issue 5880, pp. 1135
DOI: 10.1126/science.320.5880.1135c

Protein chaperones not only promote protein folding but also help to prevent protein misfolding. The GroEL-GroES chaperonin system operates as a nanomachine in the folding of proteins in Escherichia coli and contains an internal compartment thought to protect substrate proteins as they fold. Tang et al. wanted to ascertain whether this folding compartment was important in intact cells when they folded newly synthesized proteins. To do this, they generated mutant forms of the chaperone with a smaller folding compartment or whose compartment characteristics had been altered to be less amenable to the folding reaction. The viability of cells expressing the altered chaperonins was reduced when the size of the folding compartment was reduced or when the folding cavity was rendered less friendly. Despite this, for the protein substrate green fluorescent protein, the rate of folding actually increased with a slightly smaller folding cage, probably because of steric effects. Thus, even though mutant chaperonins are able to promote the folding of proteins that do not enter the folding chamber in vitro, the chamber itself is indeed critical for cell viability. — SMH

EMBO J. 27, 10.1038/emboj.2008.77 (2008).

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