Heterocomplex formation between metastasis-related protein S100A4 (Mts1) and S100A1 as revealed by the yeast two-hybrid system

S100A4 (Mts1) is a Ca2+-binding protein of the S100 family. This protein pl ays an important role in promoting tumor metastasis, In order to identify S 100A4 interacting proteins, we have applied the yeast two-hybrid system as an in vivo approach. By screening a mouse mammary adenocarcinoma library, w e have demonstrated that S100A4 forms a heterocomplex with S100A1, another member of the S100 family, The non-covalent heterodimerization was confirme d by fluorescence spectroscopy and electrospray ionization Fourier transfor m ion cyclotron resonance mass spectrometry, Mutational analysis revealed t hat replacement of Cys(76) and/or Cys(81) of S100A4 by Ser abolishes the S1 00A4/S100A1 heterodimerization, but does not affect the S100A4 homodimeriza tion in vivo. (C) 2000 Federation of European Biochemical Societies. Publis hed by Elsevier Science B.V. All rights reserved.