To obtain a high efficiency Pichia pastoris cell surface display system, two new systems based on two different anchor proteins derived from Saccharomyces cerevisiae Flo1 protein (Flo1p) were constructed respectively. The N-terminal anchor system could make the foreign lipase displayed on the P. pastoris cell surface with its C terminus free by fusion with an anchor protein containing N-terminal flocculation functional domain of Flo1p (874 residues, FS) , which was able to adhere to the cell surface via noncovalent interaction with the mannan chain of the cell wall. Conversely, the foreign lipase can kept its N terminus free in another C-terminal anchor system, which utilizes a GPI-attachment signal domain located at C-terminal region of Flo1p (1 101 residues, FL) as anchor protein. Using these systems above, recombinant R. miehei lipase with a pro region (ProRML) , which had its active site near the C-terminus, was displayed on the P. pastoris cell surface, and two surface-displayed RML, named as FSR and FLR, were obtained. Cell-surface display of the RML via Fs or FL anchor system was confirmed by flow cytometer and laser scanning confocal microscope. A strong fluorescence was clearly observed in recombinant yeast cells harboring pKFSR( pKFS-RML), but no fluorescence was detected in the yeast cells harboring pKFLR(pKFL-RML) . The hydrolytic activity of FSR reached 105. 3 U/g·[dry cell weight] with p-Nitrophenyl caprylate (pNPC) as the substrate, which is 2 times as high as that of FLR. In addition, the cell-surface display systems based on FS or FL endowed the displayed RML with different enzymatic properties. The surface-displayed RML with its C-terminus free (FSR) showed a better catalytic performance at temperature, pH and thermostability than the surface-displayed RML with its N-terminus free (FLR) did. The results suggest that the surface display of RML based on FS anchor system is more promising and more effective, especially for N-terminal immobilization of target enzyme whose catalytic site is near the C terminus.
HAN Shuang-Yan, HAN Zhen-Lin, LIN Ying, ZHENG Sui-Ping. Construction of high efficiency Pichia pastoris surface display system based on Flo1 protein[J]. Progress in Biochemistry and Biophysics,2010,37(2):200-207
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