A set of two episomal yeast expression vectors, pYME1 and pYME2, were
constructed. These Saccharomyces cerevisiae-Escherchia coli shuttle ve
ctors each contain a modified yeast MAL6S (encoding maltase) promoter
that is expressed constitutively, but is subject to carbon catabolite
repression by glucose. Expression from this promoter is still dependen
t upon the presence of active MALR (regulatory) protein. These express
ion vectors are particularly useful because most S. cerevisiae strains
are MAL(+), thereby exhibiting a wider host range than GAL-based vect
or systems. These pYME1 and pYME2 vectors are capable of expression to
levels comparable to GAL-based expression plasmids and much higher th
an a variety of other repressible promoter vectors. The vectors are id
entical, except that their multiple cloning sites (MCS) are in opposit
e orientations, making them convenient for inserting heterologous gene
s.