Purification and characterization of recombinant forms of TCL-1 and MTCP-1 proteins.

The TCL-1 gene which is located on chromosome 14 plays a major role in human hematopoeitic malignancies and encodes a 14-kDa protein whose function has not been determined. The TCL-1 gene is expressed in pre-B cells, in immature thymocytes, and at low levels in activated T cells but not in peripheral mature B cells and in normal cells. The TCL-1 protein is similar in its primary structure to a protein encoded by the mature T cell proliferation gene (MTCP-1). The MTCP-1 gene is located on the X chromosome and has been shown to be involved in rare chromosomal translocations in T cell proliferative diseases. The TCL-1 and MTCP-1 genes appear to be members of a family of genes involved in lymphoid proliferation and T cell malignancies. Our laboratory has undertaken the study of the TCL-1 and MTCP-1 proteins to determine the structure and the function of these related proteins. In the present report, we have produced, using a bacterial expression system, both purified TCL-1 and MTCP-1 proteins in forms with and without a six His tag sequence. The recombinant proteins were purified by chromatography on a Ni-NTA resin followed by reverse-phase FPLC using a buffer system at pH 7.9 and a polymeric-based reverse-phase column. The MTCP-1 recombinant proteins display greater solubility, do not form disulfide linked dimers or oligomers, and elute at a lower isopropanol concentration than the corresponding TCL-1 proteins. The purified recombinant TCL-1 and MTCP-1 proteins have been characterized by N-terminal sequence analysis, time of flight mass spectrometry, and circular dichroism spectroscopy. Initial results have indicated that the MTCP-1 protein with the His tag removed is suitable for both NMR and X-ray crystallographic methods of structure determination.