Molecular chaperones are proteins which help large molecules fold or unfold. Some help assemble or take apart other macromolecular structures. They do not occur in these structures when the structures go about their normal functions.
The first protein to be called a chaperone assists the assembly of nucleosomes from folded histones and DNA. Those assembly chaperones, especially in the nucleus, assemble folded subunits into larger structures such as cell organelles.
One major function of chaperones is to prevent polypeptide chains and assembled subunits sticking together in clumps which do not function. Some chaperones are "holdases" which act to stop aggregation. Others, called "foldases", do help fold proteins which cannot do it themselves. Such proteins violate Anfinsen's dogma.
- Hartl F.U. 1996. Molecular chaperones in cellular protein folding. Nature 381, 571–579
- 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 Biology 16 (6): 574–581. 
- Ellis R.J. 1996. Discovery of molecular chaperones. Cell stress chaperones 1 (3): 155–60.
- Richardson R.T. et al 2006. "Nuclear autoantigenic sperm protein (NASP), a linker histone chaperone that is required for cell proliferation". Journal of Biological Chemistry 281 (30): 21526–34. doi:10.1074/jbc.M603816200. PMID 16728391.
- Alekseev O.M. et al 2009. "Analysis of gene expression profiles in HeLa cells in response to overexpression or siRNA-mediated depletion of NASP". Reproductive Biology and Endocrinology 7: 45. doi:10.1186/1477-7827-7-45. PMC 2686705. PMID 19439102.
- Ellis R.J. 2006. "Molecular chaperones: assisting assembly in addition to folding". Trends in Biochemical Sciences 31 (7): 395–401. doi:10.1016/j.tibs.2006.05.001. PMID 16716593.
- Kris Pauwels et al 2007. "Chaperoning Anfinsen: the dteric foldases". Molecular Microbiology 64 (4): 917. doi:10.1111/j.1365-2958.2007.05718.x. http://ultr23.vub.ac.be/ultr/pub/pdfs/290.pdf.