HIGH-LEVEL SECRETION OF CORRECTLY PROCESSED BETA-LACTAMASE FROM SACCHAROMYCES-CEREVISIAE USING A HIGH-COPY-NUMBER SECRETION VECTOR

We have sought to obtain a convenient system for the high-level produc tion of secreted proteins in yeast. With the aid of a secretion report er cassette we examined the secretion of beta-lactamase (Bla) as a mod el protein and found the highest expression in Saccharomyces cerevisia e using a high-copy-number plasmid. We further developed the high-copy -number plasmid introducing a secretion cassette that has a convenient cloning site coinciding with the sequence encoding the KEX2 cleavage site. Large quantities of correctly-processed product can therefore be obtained. We show that 0.3 g/l of correctly processed beta-lactamase can be obtained in fed-batch cultures without the need for selective m edia or significant loss of the plasmid.