Recombinant rat fibroblast growth factor-16: Structure and biological activity

Fibroblast growth factor-16 (FGF-16) is the most recent member of the FGF f amily to be cloned. Since the biologic activity of rat FGF-16 (rFGF-16) was unknown, and this protein has no apparent signal sequence, we transformed its entire cDNA into Escherichia coli for high-level expression and further characterization of this novel protein. an attempt was made to purify the expressed protein from the supernatant of mechanically lysed cells using se quential cation-exchange chromatography. This resulted in a gradual loss of the protein as precipitate throughout the purification process. In additio n to precipitation during purification, sodium dodecyl sulfate polyacrylami de gel electrophoresis revealed that the partially purified materials showe d a cluster of protein bands around 20k to 29k. Sequence analysis of the ma jor bands indicated that two N-terminal truncations had occurred, during E. coli fermentation, purification, or both. The largest truncation resulted in the removal of the 34 N-terminal amino acids, including the initiation c odon methionine. We cloned d34 rFGF-16, expressed the gene in E. coli, and developed a purification process for this form. Even with this truncated fo rm, precipitation was a problem. We were largely able to overcome this prob lem, however, by including EDTA throughout the purification process. We hav e characterized the structure of purified d34 rFGF-16 extensively using cir cular dichroism, Fourier transform infrared spectroscopy, and sedimentation velocity analysis. These studies revealed that the protein has a distinct tertiary structure, consists primarily of beta-strands, has a weak tendency to self-associate, and is fairly extended. We then performed biologic assa ys which showed that d34 rFGF-16 induces oligodendrocyte proliferation in v itro, and induces hepatocellular proliferation and increased liver weight i n vivo. Tn summaryZ FGF-16, a novel FGF family member, has both unique stru ctural and biological properties. (C) 1999 Academic Press.