Threonine-poor apolipoprotein,

ApoSAA, normally a trace component of plasma, is an acute-phase plasma protein, that is, one that is elevated in a variety of disease states (R18). Its identification is interesting. A small protein of 76 residues, now called protein AA, was identified during the study of the proteins present in extracellular amyloid deposits in the type of amyloidosis particularly associated with inflammation (B24, H36, Lll, S38), Antibodies to protein AA reacted with two AA-related proteins in plasma, one of approximate Mr 180,000 (SAA) and the other found in HDL of Mr 14,000-15,000 or 12,000 (apoSAA) (A19, B25, B26, L12, L15). The N-terminal 76-amino-acid portion of apoSAA is identical to that of amyloid protein AA (E8). Human apoSAA has now been sequenced and has been shown to consist of 104 amino acid residues (B27). Further studies in man have demonstrated microheterogeneity in apoSAA (B18, B19, M30) and Benditt et al. describe specific amino acid substitutions (B27, P6). Shore et al. have described a second similar threonine-poor apolipoprotein, apparently a dimer of Mr 40,000... 

Shore, V. G., Shore, B., and Lewis, S. B., Isolation and characterization of two threonine-poor apolipoproteins of human plasma high density lipoproteins. Biochemistry 17, 2174-2179 (1978). 

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