protein solubility in TCA - PRPs have special properties? (Jan/20/2005 )

Hi
I am working with salivary proteins and I saw, several times, protocols in which the proline rich proteins are isolated by mixing the saliva sample with an equal volume of TCA 10%. I do not understand the basis for that. Can someone explain me why this type of proteins are soluble in TCA? What makes them different from the other proteins?
Thank you
ecsl

TCA is used for two purposes- to remove nucleic acids by precipitation and to make the otherwise insoluble proline rich proteins more soluble-does not always work because every protein is different. You don't have to use this method. Nucleic acids can be removed by adding trace amounts of RNaseI and DNaseIII- while proline rich proteins go into solution at 0.75M NaCl strength in any pH 8.0 buffer.