Buffered non-fermenter system for lab-scale production of secreted recombinant His-tagged proteins in Saccharomyces cerevisiae.

Expression of recombinant proteins using a secretion system can minimize co-purification of contaminating host proteins. Production of His-tagged recombinant proteins in the yeast alpha-factor secretion system has previously required a fermenter system to control the growth conditions such as pH of the yeast culture. We describe an inexpensive non-fermenter system for the production of secreted recombinant His-tagged proteins in Saccharomyces cerevisiae that uses a buffered low peptone YP glycerol medium, which does not interfere with immobilized metal affinity chromatography. Maspin, a tumor suppressor serpin, was expressed as a secreted N-terminal His/FLAG-tagged protein. Purification of the soluble active recombinant protein only requires centrifugation, concentration by ultrafiltration, and Ni2+ affinity chromatography. Purified protein yields of this system are 3-5 mg/L culture medium.