Immunological identity of rat liver cytosolic heme-binding protein with purified and recombinant liver fatty acid binding protein by western blots of two-dimensional gels.

We examined the degree of similarity between rat liver cytosolic heme-binding protein (HBP) and rat liver fatty acid binding protein (L-FABP) purified from rat liver cytosol and recombinant L-FABP (rL-FABP). We compared 1) HBP, 2) L-FABP, and 3) rL-FABP prepared in three different laboratories and probed them with three different antisera also from different laboratories on Western blots. The objective was to determine whether the isoform pattern of the recombinant would resemble those of the purified rat liver proteins and whether heme is bound by the isoforms. To investigate the similarities, we compared the immunoreactivity of purified HBP, L-FABP, and rL-FABP by probing Western blots of 2-D gels with polyclonal antibodies raised against each of these proteins. All of the antibodies react with the same isoelectric species for each of the proteins. In addition, [55Fe]-heme binds equally well to the 2 major HBP isoforms.