CHARACTERIZATION AND CRYSTALLIZATION OF RECOMBINANT HUMAN NEUROTROPHIN-4

Neurotrophin-4 (NT-4) is the most recently discovered member of the ne urotrophin family. We have expressed, refolded, and purified recombina nt human NT-4 from Escherichia coli and compared it with recombinant h uman NT-4 secreted into the culture medium of baculovirus-infected ins ect cells. Both preparations were characterized and determined to be i ndistinguishable according to several biochemical criteria. Recombinan t NT-4 from E. coli was crystallized in a form suitable for x-ray anal ysis, and characterization of these crystals indicated that NT-4 was p resent as a dimer within the asymmetric unit. NT-4 was active in promo ting the survival of rat TrkB receptor-expressing fibroblasts, but was inactive on embryonic chicken sensory neurons, unlike the other membe rs of the neurotrophin family and in contrast to the reported activiti es of partially purified NT-4.