Monday, November 24, 2008

cells need chaperones

Yes, you read that right – cells need chaperones! Cellular chaperones are of course different from the social chaperones that we are familiar with. However, to a certain extent, both kinds of chaperones actually perform similar functions. While a social chaperone ensures that the concerned parties (usually unmarried ladies or gents) behave properly during social occasions, the cellular chaperones also make sure that certain molecules in the cell (especially proteins and nucleic acids) behave properly.

So far, four instances have been discovered wherein chaperones are needed by the cell, but the list may still increase.

The first instance is in the association of the genetic material with histone proteins. When DNA, the genetic material associates with histone proteins as they fold together to form the chromosomes, chaperones make sure that folding is correct.

Second, most chaperones are actually heat shock proteins. Huh? What are those? Well, in the presence of heat and stress, proteins usually tend to misfold and aggregate. The heat shock proteins or chaperones try to prevent this misfolding because protein function is dependent on their proper folding. Once they are misfolded they lose their ability to function properly. One example of a disorder that can happen when proteins are misfolded is mad cow’s disease.

The third instance when chaperones are needed is during the formation of new proteins. As the polypeptide chains exit from the ribosomes during their synthesis, chaperones guide them to fold properly into fully functional proteins.

Lastly, chaperones guide polypeptides as they are transported across the membranes of the mitochondria and ER. The chaperones make sure that the polypeptide chains pass through the membrane properly before they fold over.

As you can see cellular chaperones just like their social counterparts also ensure proper behavior of their molecular protégés.

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