A model system for the investigation of heterologous protein secretion pathways in Lactococcus lactis

J.M. Wells*, P.W. Wilson, P.M. Norton, R.W.F. Le Page

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

31 Citations (Scopus)


The capacity of recombinant strains of Lactococcus lactis to secrete a heterologous protein was investigated by constructing two expression- secretion vectors (pLET2 and pLET3) for use with a lactococcal gene expression system driven by the highly active T7 RNA polymerase. The vectors incorporated different lactococcal secretion leaders and translation initiation sequences. When tetanus toxin fragment C (TTFC) was used as a test protein, the quantities of TTFC produced by the pLET2-TTFC strain exceeded the rate of secretion of TTFC into the growth medium. However, nearly all of the soluble TTFC associated with the cell (3.4%) was translocated through the cell membrane. The pLET3-TTFC strain did not accumulate TTFC intracellularly and exhibited growth characteristics and viability identical to the growth characteristics and viability of the control strain. This strain secreted approximately 2.9 mg of TTFC per liter into the growth medium after 6 h of growth under test tube conditions. Our results indicate that L. lactis is capable of secreting substantial amounts of heterologous protein and also confirm the findings of other workers that the cell wall may serve as a functional barrier to the diffusion of some secreted proteins into the growth medium.

Original languageEnglish
Pages (from-to)3954-3959
Number of pages6
JournalApplied and Environmental Microbiology
Issue number11
Publication statusPublished - Nov 1993
Externally publishedYes


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