Saccharomyces cerevisiae strains that overexpress heterologous proteins.

We describe a system that facilitates the selection of host mutants that overproduce a range of secreted and internally produced heterologous proteins in Saccharomyces cerevisiae. These mutants were initially selected for their ability to oversecrete recombinant human albumin (rHA), as detected by a direct visual assay that relies upon antibody precipitation in solid media. Yeast strains that were able to synthesize and secrete increased levels of rHA also produced elevated levels of internally expressed proteins including alpha 1-antitrypsin Pittsburgh variant and plasminogen activator inhibitor type 2.