Objective: To obtain recombinant human SDF-1β expressed in E. coli and purify SDF-1β with biological activity from the bacterium. Methods: A thioredoxin-SDF-1β fusion protein (26 × 103) composed of230 amino acid residues was expressed in E. coli AD494 (DE3)pLysS under the induction of IPTG when pET32a(+)-SDF-1β was used as an expression vector. Purified SDF-1β was produced through following procedures: Bacteria lysis, metal-chelated affinity chromatography (MAC), enterokinase digestion to separate SDF-1β from fusion protein, cation exchange chromatography (CEC) and reverse-phase high performance liquid chromatography (RP-HPLC). Western blot with anti-SDF-1β monoclonal antibody (mAb), N-terminal amino acid sequencing, ligand-binding assay and cytosensor/microphysiometry were used to investigate the biochemical characters and biological activities of the purified SDF-1β. Results: From 10% to 15% of total bacterium protein was expressed as fusion protein. Approximately 400μg purified SDF-1β (7. 8 × 103) consisting of 71 amino acid residues were produced from 1 L of fermented bacteria. Western blot showed that anti-SDF-1β mAb bound with the purified SDF-1β specifically. N-terminal amino acid sequencing indicates that N-terminus of purified SDF-1β possessed as the same amino acid sequence as nature one. Purified SDF-1β not only had the binding activity with CXCR4 expressing cells [Kd = ( 12.20± 2. 99) nmol/L ], but also activated CXCR4 expressing cell signaling specifically in a dose-dependence manner. Conclusion: The purified recombinant human SDF-1β produced with this method possesses biochemical characters and biological activities as same as those nature human SDF-1β.
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