Human serum amyloid A protein. Behaviour in aqueous and urea-containing solutions and antibody production
Human serum amyloid A protein (apo-SAA) can be prepared by gel filtration of delipidated acute-phase high-density lipoprotein in the presence of urea. The resultant apo-SAA is soluble (>90% solubility) in a wide range of buffer solutions, with all of the six major isoforms of apo-SAA being equally soluble. In urea-containing solutions the isoforms behave qualitatively differently in various urea concentrations, probably reflecting subtle primary-structure variations. The higher-pI isoforms are only completely unfolded at >7 M-urea. By immunizing with apo-SAA adsorbed to acid treated bacteria (Salmonella minnesota R595), high-titre antibodies can easily be elicited in rabbits.