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 degrees C and below, above 58 degrees 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 degrees 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.