Serum amyloid A (SAA) is often used as a non-specific marker of inflammation. Its concentration in blood increases in response to inflammatory stimulus such as tissue injury, infection or trauma. SAA proteins are encoded by four different genes, SAA1-SAA4. In human beings, SAA1 and SAA2 belong to the group of major acute phase proteins similarly to C-reactive protein. SAA4 is constitutively expressed and the gene encoding for SAA3 is considered to be a pseudogene.
SAA1 and SAA2 proteins are highly homologous. Their sequence identity is over 92 %.
We now provide both SAA1 and SAA2 as recombinant antigens. The antigens do not contain any affinity tags. They have been expressed in E. coli and purified under non-denaturing conditions to homogeneity (see Figure 1). The purity of the proteins exceeds 95%. Both recombinant antigens could be used as calibrators or standards in SAA immunoassays (see Figure 2).
Figure 1. Tricine-SDS-PAGE of purified SAA1 and SAA2 (5 μg/lane) under reducing conditions. Gels were stained using SYPRO Ruby.
Figure 2. The calibration curves with recombinant SAA1 and SAA2 as antigens for VSA25-VSA31 assay.