Effect of the Membrane\nInsertase YidC on the Capacity\nof Lactococcus lactis to Secret Recombinant\nProteins

Lactococcus lactis is\na crucial\nfood-grade cell factory for secreting valuable peptides and proteins\nprimarily via the Sec-dependent pathway. YidC, a membrane insertase,\nfacilitates protein insertion into the lipid membrane for the translocation.\nHowever, the mechanistic details of how YidC affects protein secretion\nin L. lactis remain elusive. This study\ninvestigates the effects of deleting <i>yidC1</i>/<i>yidC2</i> on L. lactis phenotypes\nand protein secretion. Compared to the original strain, deleting <i>yidC2</i> significantly decreased the relative biomass, electroporation\nefficiency, and F-ATP activity by 25%, 47%, and 33%, respectively,\nand weakened growth and stress resistance, whereas deleting <i>yidC1</i> had a minimal impact. The absence of either <i>yidC1</i> or <i>yidC2</i> reduced target proteins\nsecretion. Meanwhile, there is a considerable alteration in the transcription\nlevels of genes involved in the secretion pathway, with <i>secY</i> transcription increasing over 135-fold. Our results provide a theoretical\nfoundation for further improving target protein secretion and investigating\nthe YidC function.