Transforming growth factor beta 1: NMR signal assignments of the recombinant protein expressed and isotopically enriched using Chinese hamster ovary cells.

The transforming growth factor 8s are a homologous family of multifunctional cytokines that regulate cell growth and differentiation. As a prelude to studies of the solution structure and dynamics of TGF-81, we report virtually complete assignment of 'H and 15N resonances for this 25-kDa homodimeric protein. Recombinant TGF-81 was expressed in Chinese hamster ovary cells. The cells were grown either in a completely 15N-enriched medium or in a medium containing selectively 13C,15N-labeled amino acids to obtain either uniformly or specifically labeled protein, respectively. Two- and three-dimensional heteronuclear edited magnetic resonance spectra of the uniformly 15N-labeled protein and three samples selectively labeled with 13C and 15N yielded assignments for 96% of the backbone amide and Ca protons and 87% of the side chain protons. To our knowledge, this is the first report of the use of an animal cell expression system to obtain extensive isotopic enrichment in order to sequentially assign a protein. The methodology described herein for the isotopic enrichment and resonance assignments of TGF-81 should be generally applicable to other eukaryotic proteins expressed by animal cells. The transforming growth factor Bs (TGF-Ps)' are important regulators of numerous physiological processes including normal tissue growth and wound repair (Roberts & Sporn, 1990; Sporn & Roberts, 1990; Massagub, 1990). The diverse activities of these proteins include their ability to act as multifunctional regulators of the growth and differentiation of many types of cells. The TGF-Bs are important in maintenance of normal epithelial structures, in the formation and repair of connective tissue and bone, and in the formation and function of the cells of the blood and the immune system. TGF-@s and their receptors are present in nearly all cells. Five homologous forms of TGF-19 have been characterized, two of which have been isolated from natural sources in significant quantities: TGF-01 and TGF-82. TGF-B1 was originally isolated from human platelets but also has been purified from additional sources including bovine kidney, bovine bone, and porcine platelets. Recently, TGF-B1 has been cloned and