Molecular cloning and sequencing of equine cDNA encoding serum amyloid A (SAA)

The serum amyloid A (SAA) protein is a characteristic and sensitive acute p hase reactant in all vertebrates investigated. We molecularly cloned the eq uine cDNA encoding SAA from the liver of a healthy horse by polymerase chai n reaction (PCR). The cloned cDNA is 480 bases in length, and contains an o pen reading frame (ORF) of 387 nucleotides encoding a precursor SAA protein of 128 amino acids. The precursor of horse SAA seems to have an 18-residue signal peptide and differs from the reported amino acid sequences of the h orse SAA by substitution of valine at residue 81. It shows high homology wi th SAA amino acid sequence of other species such as dog (80.6%), mink (77.5 %), human (76.9%) and duck (71.9%). An insertion of eight amino acids at re sidues between 85 and 92, as compared to human SAA, has also been found in horse SAA. The availability of the equine SAA cDNA will provide a useful re agent for studying its role in diseased horses. (C) 2000 Elsevier Science B .V. All rights reserved.