Structural investigation of tumor differentiation factor

Abstract

Tumor differentiation factor (TDF) is a 17 kDa protein produced by the pituitary and secreted into the bloodstream, with no definitive function and incomplete characterization. TDF has the following four cysteine (Cys) residues: Cys17, Cys70, Cys97, and Cys98. To understand the function of TDF, we (1) overexpressed and characterized recombinant TDF (rTDF); (2) investigated native, secreted TDF; and (3) assessed potential disulfide connectivities using molecular modeling. Our results from Western blotting (WB) experiments suggest that rTDF is mostly expressed as insoluble, monomeric, and dimeric forms. Mass spectrometry analysis of the overexpressed rTDF identified a peptide that is a part of TDF protein. WB of the native, secreted TDF detected it as a 50 kDa band. In addition, investigation of TDF by molecular modeling suggests that the Cys residues may form disulfide bridges between Cys17-Cys98 and Cys70-Cys17. © 2012 International Union of Biochemistry and Molecular Biology, Inc.