Kluyveromyces lactis gene KlBIM1 in high copy state suppresses heterologous protein secretion

2 Vilnius University, Department of Botany and Genetics, Vilnius, Lithuania The aim of this work was to investigate the genes that under over-expression in the yeast Kluyveromyces lactis decrease the yield of secretory proteins. The MD2/1-9 mutant strain with an enhanced ability to secrete different proteins was used. The genes suppressing the protein secretion process were detected by using the α-amylase gene. The gene KlBIM1 was found to suppress mutation of the MD2/1-9 mutant strain in yeast K. lactis. To test the influence of the chromosomal gene on protein secretion, the BIM1 gene was disrupted in both yeast K. lactis and S. cerevisae, and the influence of disruption on the protein secretion process was evaluated. The disruption of the gene KlBIM1 had no influence on the protein secretion process in K. lactis, however, disruption of the BIM1 gene in S. cerevisiae elevated protein secretion by approximately 24%. Our experiment has shown that K. lactis strain lacking the gene KlBIM1 is not suitable for elevated heterologous protein secretion. The K. lactis mutant strain MD2/1-9 was transformed by the S. cerevisiae gene BIM1 in order to evaluate the influence of this gene in a high-copy state to the α-amylase secretion process. The S. cerevisiae gene BIM1 in a high-copy-number state significantly decreased secretion of α-amylase in K. lactis MD2/1-9. This fact suggests that the homology between the gene KlBIM1 in K. lactis and BIM1 in S. cerevisiae is rather high and the biological function of those genes in both yeasts is quite similar.