Identification of parvalbumin alpha in bovine hypothalamus: a partial primary structure

Macrophage migration inhibitory factor: identification of the 30-kDa MIF-related protein in bovine brain

Macrophage migration inhibitory factor (MIF) is a ubiquitous protein playing various immunologic, enzymatic, and hormonal roles. MIF was originally identified for its capacity to inhibit the random movement of macrophages in vitro. MIF is widely expressed in many tissues with particularly high levels in the nervous system. Using the reversed-phase HPLC, N-terminal microsequence analysis, and database searching, we have identified in bovine brain several MIF-like proteins. According to mass spectral analysis, the molecular masses for three of them were determined as 12,369.2, 12,299.7, and 9,496.2 Da. In addition, we have identified another MIF-related protein (29,568.9 Da) by Western blotting using anti-MIF antibody raised to MIF (having an apparent molecular weight of 12 kDa) isolated to homogeneity from bovine brain cytosol. The modified purification procedure was mainly based on exclusion- and ion-exchange chromatography. Using p-hydroxyphenylpyruvic acid as a substrate, we have demonstrated tautomerase activity of the isolated MIF. The N-terminal sequences for all MIF-like proteins were found to be identical. Several other higher molecular weight putative MIF-related proteins were also revealed in the bovine brain cytosol extract. A multifunctional nature of MIF is suggested to be a result of its occurrence in different oligomerization states in a wide variety of tissues and cells.

Identification of macrophage migration inhibitory factor isoforms in bovine brain

In the course of the study of the primary structures and molecular mechanisms of action of immunologically active compounds of the nervous system we have isolated from the soluble fraction of total bovine brain two heat-stable proteins. The purification procedure was mainly based on DEAE-Servacel ion-exchange chromatography and reversed-phase HPLC. The proteins were identified by the N-terminal Edman microsequence analysis and database searching as macrophage migration inhibitory factor (MIF). The N-terminal sequences for MIF1 and MIF2 were found to be identical. According to mass spectral analysis, the molecular masses for MIF1 and MIF2 were determined respectively as 12,369.21 and 12,299.7 Da. In addition, we have also isolated a third peptide having the same N-terminal sequence and Mr 9,496.2 that seems to be a proteolytic fragment of MIF. Using p-hydroxyphenylpyruvate as a substrate, we have not revealed tautomerase activity of either MIF1 or MIF2. As both the immunologic and enzymatic activities were reported to be expressed by the oligomeric structure of MIF, we suggest that the present study may give additional information on MIF in terms of structural properties of this protein. A comparatively simple purification procedure is presented that may be widely used for simultaneous isolation in one run of MIF isoforms.