Glutathione binding rat liver 13k protein is the homologue of the macrophage migration inhibitory factor

We have cloned the cDNA of the rat liver 13k protein, that has glutathione binding activity, from a rat liver cDNA library. The nucleotide sequence of this cDNA predicts a protein of 115 amino acids. This protein has 99.1%, 89.6% and 73.0% homology with mouse, human and chicken macrophage migration inhibitory factor (MIF), respectively. This indicates that the rat liver 13k protein is homologue of the MIF. The N-terminal 25 amino acids show 35% sequence similarity with that of the rat glutathione transferase Yb subunit. Although the remaining C-terminal sequence has no sequence identity with glutathione transferase Yb subunit, about 50% homology was found, if conservative substitutions and gaps were taken into account. Northern blot analysis indicates that this gene is expressed in a wide variety of organs including brain, spleen, liver, muscle and kidney. Southern blot analysis suggests that the MIF gene has many pseudo-genes or/and closely related genes.