Abstract: To analyze the characteristics and function,we cloned the complete 1284 bp CDS of the sulfide quinone reductase (SQR) gene from Rhodobacter capsulatus DSM1710. Then the prokaryotic expression vector pRSETA-SQR for the SQR gene was successfully constructed. Expression of pRSETA-SQR fusion protein with a molecular mass of approximately 50 ku in Escherichia coli BL21(DE3) induced by IPTG was confirmed by SDS-PAGE and Western blotting. The SDS-PAGE result indicated that with the induction of 0.4 mmol/L IPTG for 6 h at 37 ℃,the fusion protein of the SQR was expressed well. The fusion protein was expressed as inclusion body. The purification and renaturation results showed that the SQR recombinant protein had the bioactivity and could digest the substrate decylubiquinone (decyl-UQ). The enzyme activity was measured with Km value of about four.

Key words: Rhodobacter capsulatus; sulfide-quinone reductase(SQR) gene; gene cloning; prokaryotic expression; bioactivity