Improved preparation and crystallization of 25 kDa human fibroblast growthfactor-9

We prepared 25 kDa human fibroblast growth factor-9 (hFGF-9 N33) on a large scale after overproduction in Escherichia coli MM294 (DE3)/pTG931. The pur ification was performed by a combination of hydrophobic chromatography and HPLC with an ion exchange column, a heparin affinity column and a gel filtr ation column. This improved procedure was rapid and simple, and the purifie d hFGF-9 N33 was found to be homogeneous as judged by various criteria, suc h as amino acid analysis, hi-terminal amino acid sequence, C-terminal amino acid analysis and biological activity. Furthermore, as determined by low e ndotoxin and DNA content, the protein was of high purity. In addition, the hFGF-9 N33 prepared in the present study was easily crystallized by the vap our diffusion method.