Elevated extrahepatic expression and secretion of mammary-associated serum amyloid A 3 (M-SAA3) into colostrum

Thomas L. McDonald, Marilynn A. Larson, David R. Mack, Annika Weber

Research output: Contribution to journalArticlepeer-review

185 Scopus citations


Mammary-associated serum amyloid A 3 (M-SAA3) was secreted at highly elevated levels in bovine, equine and ovine colostrum and found at lower levels in milk 4 days postparturition. N-terminal sequencing of the mature M-SAA3 protein from all the three species revealed a conserved four amino acid motif (TFLK) within the first eight residues. This motif has not been reported to be present in any of the hepatically-produced acute phase SAA (A-SAA) isoforms. Cloning of the bovine M-Saa3 cDNA from mammary gland epithelial cells revealed an open reading frame that encoded a precursor protein of 131 amino acids which included an 18 amino acid signal peptide. The predicted 113 residue mature M-SAA3 protein had a theoretical molecular mass of 12,826 Da that corresponded with the observed 12.8 kDa molecular mass obtained for M-SAA3 in immunoblot analysis. The high abundance of this extrahepatically produced SAA3 isoform in the colostrum of healthy animals suggests that M-SAA3 may play an important functional role associated with newborn adaptation to extrauterine life and possibly mammary tissue remodeling.

Original languageEnglish (US)
Pages (from-to)203-211
Number of pages9
JournalVeterinary Immunology and Immunopathology
Issue number3-4
StatePublished - 2001


  • Bovine cDNA
  • Colostrum
  • Extrahepatic serum amyloid A
  • Serum amyloid A 3

ASJC Scopus subject areas

  • Immunology
  • veterinary(all)


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