Temperature-Induced Dissociation of Serum Amyloid Protein SAA

Serum amyloid A protein (SAA) has been shown to be unstable at elevated temperatures. While in agreement with earlier reports, molecular weights of approximately 180,000 daltons were determined by gel filtration at 37°C and below, above 38°C additional AA-antigenic activity was found in the void volume and at the position of approximately 12,000 daltons. The latter polypeptide resembled in size and immunoreactivity SAAL in that it had AA-antigenic determinants exposed at 4°C (unlike SAA). Because the release of SAAL or a similar molecule could not be prevented by the enzyme inhibitor PMSF, a temperature-dependent dissociation of SAA is proposed.

In view of the known occurrence of amyloid following febrile conditions, the change in size and immunoreactivity of AA-antigenic proteins in vitro may indicate that a similar mechanism in vivo is important in the genesis of AA-type amyloidosis.