Chaperonin (GroEL-GroES) / ADP complex
Escherichia coli (bacteria)
Dictionaries define chaperones as people, usually older or married women, who accompany young people, especially young women, in public to ensure that they behave properly. This inspired to give the name chaperonin to a class of proteins which assist in the proper three-dimensional folding of other proteins. DNA stores the information about proteins in genes, strands of DNA. Three consecutive base pairs on the DNA correspond to one particular amino acid. With the help of RNA this information is then used to synthesize the protein on a large structure, the ribosome, as a linear chain of amino acids. In principle, the three-dimensional structure of proteins is determined by their amino acid sequence and once synthesized, they fold into their correct shape. Sometimes however, this folding step fails. The protein misfolds and aggregates irreversibly. To minimize the occurrence of this event, nature has invented a tool to help the protein fold correctly. This tool is the chaperonin protein seen here.
The GroEL-GroES complex is a very large structure with almost 60000 atoms, shaped like a tall hat. Seven GroEL molecules form a torus-shaped ring and two such rings, a total of 14 GroEL molecules, form the bottom of the hat with a diameter of about 140 angstrom and a height of about 150 angstrom. At the top sit seven GroES molecules closing the hat, with a diameter of 80 angstrom and a height of about 30 angstrom. The height of the whole molecules is about 185 angstrom. Inside the complex, along the axis of sevenfold symmetry, is a large cylindrical cavity, about 50-60 angstrom in diameter and about 150 angstrom long. At the tip of the hat is a circular hole with a diameter of about 10 angstrom. The size of the cavity is such that proteins can fit into it easily and interact with the surface residue on the inside of the cavity. The GroEL-GroES complex is capable of large-scale motion of its parts, to accomplish its folding support function. The energy for this action is generated by the conversion of nature's standard fuel, adenosine triphosphate (ATP) into adenosine disphosphate (ADP) and the structure shown here contains the end-product, ADP (as seen in Fig.1).
Protein Data Bank (PDB)
author: Arno Paehler