Holin‐assisted bacterial recombinant protein export

Abstract

A simple generic method for enhancing extracellular protein yields in engineered bacteria is still lacking. Here, we demonstrated that phage‐encoded holin can be used to export proteins to the extracellular medium in both Gram‐negative Escherichia coli and ‐positive Lactococcus lactis. When a putative holin gene LLNZ_RS10380 annotated in the genome of L. lactis NZ9000 (hol380) was recombinantly expressed in E. coli BL21(DE3), the Hol380 oligomerized up to hexamer in the cytoplasmic membrane, yielding membrane pore to allow the passage of cytosolic β‐galatosidase (116 kDa), whose extracellular production reached 54.59 U/μl, accounting for 76.37% of the total activity. However, the overexpressed Hol380 could not release cytosolic proteins across the membrane in L. lactis NZ9000, but increased the secretory production of staphylococcal nuclease to 2.55‐fold and fimbrial adhesin FaeG to 2.40‐fold compared with those guided by signal peptide Usp45 alone. By using a combination of proteomics and transcriptional level analysis, we found that overexpression of the Hol380 raised the accumulation of Ffh and YidC involved in the signal recognition particle pathway in L. lactis, suggesting an alternative road participating in protein secretion. This study proposed a new approach by expressing holin in bacterial cell factories to export target proteins of economic or medical interest.

Virulent Phage vB_EfaS_WH1 Removes Enterococcus faecalis Biofilm and Inhibits Its Growth on the Surface of Chicken Meat

“…Phage WH1 has a broad cleavage spectrum, which is related to the fact that its tail fiber can recognize a variety of host receptor proteins and may also be particularly effective in the lysin encoded by ORF60 in the WH1 genome. Holin (ORF42) is a perforin protein that penetrates the cell membrane and inserts itself into bacteria [ 49 ]. Therefore, WH1 may use the holin–endolysin tactics to lyse the host cell and release lytic virions [ 50 ].…”