Molecular chaperones definitions

The above definition of molecular chaperone is entirely fnnctional and contains no constraints on the mechanisms by which different chaperones may act. The term noncovalent is nsed to exclude those proteins that carry out posttranslational covalent modifications. Protein disulfide isomerise may seem to be an exception, bnt it is both a covalent modification enzyme and a molecular chaperone. It is helpful to think of a molecnlar chaperone as a fnnction rather than as a molecnle. Thns, no reason exists why a chaperone function shonld not be a property of the same molecnle that has other fnnctions. Other examples include peptidyl-prolyl isomerase, which possesses both enzymatic and chaperone activities in different regions of the molecnle, and the alpha-crystallins, which combine two essential fnnctions in the same molecnle in the lens of the eye-contribnting to the transparency and the refractive index reqnired for vision as well... 

Spiro, R. G., Zhu, Q., Bhoyroo, V., and Soling, H.-D. (1996). Definition of the lectin-like properties of the molecular chaperone, calreticulin, and demonstration of its copurification with endomannosidase from rat liver Golgi. J. Biol. Chem. 271, 11588-11594. 

Based on all these results lipids can function as non-protein molecular chaperones or lipochaperones that specifically mediate the folding of proteins thereby extending the definition of chaperones to other biomolecules in addition to proteins (Bogdanov and Dowhan, 1999). 

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