The structure of the chaperonin complex of the bacteria Thermus thermophilus reveals clues about how the important molecule may do its job of folding new or damaged proteins within cells.

Led by Professor So Iwata of Imperial College London, the team of scientists announce their findings in this month's edition of the journal Structure (August 2004).

The complex comprises three separate parts - two identical 'cage' units lashed back to back, and a 'cap' unit that sits atop the cage, acting as a stopper. The cage contains the unwound, or denatured, protein, while the chaperonin goes about refolding its shape using the cellular energy source, ATP.

The structure of the chaperonin complex is one of the largest and most difficult solved by scientists. Each unit of the cage or cap is made up of seven separate polypeptide chains.

"It's huge," said Professor Iwata. "The cavity can accommodate even very large proteins inside. It makes the perfect environment for the protein to fold."

It is the second structure of a chaperonin complex to be reported by scientists, and is visualised at a resolution of 2.8 Angstroms. The first was published in 1997 by the group of the late Professor Paul Sigler at Yale University, USA.

Unlike the first structure, taken from the chaperonin of gut bacterium Escherichia coli, the Thermus thermophilus structure is a more natural structure revealing the irregular oval interior of the cage's subunits.

Thermus thermophilus is a highly thermophilic bacteria, first found living in deep-sea hot vents. It contains proteins thought to be very similar to those found in the energy powerhouses of plant and animal cells, the mitochondria.

Immediately, the largest users of this new knowledge are biochemists working on the protein and bioinforma
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17-Aug-2004