Each protein exists as an unfolded polypeptide or random coil when translated from a sequence of mRNA to a linear chain of amino acids. This polypeptide lacks any developed three-dimensional structure (left hand side of the top figure).
Amino acids interact with each other to produce a well-defined three-dimensional structure, the folded protein (right hand side of the figure). This is known as the native state. The resulting three-dimensional structure is determined by the amino acid sequence (Anfinsen's dogma).[3]
Without its correct three-dimensional structure a protein does not work. However, some parts of proteins may not fold: this is normal.[4]
If proteins do not fold into their native shape, they are inactive and are usually toxic. Several diseases may be caused by misfolded proteins.[5] Many allergies are caused by the folding of the proteins, for the immune system does not produce antibodies for all possible protein structures.[6]
Chaperonins are large proteins which help the folding of some proteins after synthesis.[9] Chaperones in general were first discovered helping histones and DNA join up to form nucleosomes.[10] Nucleosomes are the building blocks for chromosomes. This is the way many cell organelles are built up.[11][12]
↑Dobson C.M. 2000. The nature and significance of protein folding. In Pain R.H. (ed) Mechanisms of protein folding. Oxford University Press, 1–28. ISBN0-19-963789-X
↑Bartlett A.L. & Radford S.E. 2009. An expanding arsenal of experimental methods yields an explosion of insights into protein folding mechanisms. Nat. Struct. Mol. Biol. 16, 582–588
↑Hartl F.U. & Hayer-Hartl M. 2009. Converging concepts of protein folding in vitro and in vivo. Nature Structural & Molecular Biology16 (6): 574–581. [1]