Localization of four human serum amyloid A (SAA) protein superfamily genes to chromosome 11p: characterization of a fifth SAA-related gene sequence.

The serum amyloid A proteins (SAAs) are heterogeneous differentially expressed apolipoproteins of M(r) 12-19 kDa. Four SAA loci have been described. Two of the loci (SAA1 and SAA2) encode acute-phase SAAs (A-SAAs), which exhibit a dramatic transient increase in serum concentration in response to inflammatory stimuli; a third locus (SAA3) defines a pseudogene; and a fourth locus (SAA4) encodes a constitutively expressed SAA (C-SAA). Using locus-specific polymerase chain reaction, we have definitively assigned all four well-characterized SAA loci, SAA1, -2, -3, and -4, to chromosome 11p. In addition, we have more fully characterized an ill-defined sequence previously misidentified by others as SAA4, which also maps to chromosome 11p and may represent a fifth SAA locus.