Recombinant TRb1 protein is isolated from an E. coli strain that carries the coding sequence of the human TRb1 isoform under the control of a T7 promoter (accession number NM 000461) and purified by a combination of affinity and gel filtration chromatography. TRa1 protein has an amino terminal polyhistidine tag and is purified free of contaminating proteases, endonucleases and exonucleases, and is visually determined to be > 95% pure on an SDS-polyacrylamide gel.
