Another Breaker of the Wall: the Biological Function of the Usp45 Protein of Lactococcus lactis

Jhonatan A Hernandez-Valdes, Chenxi Huang, Jan Kok, Oscar P Kuipers*

*Corresponding author for this work

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Abstract

Lactococcus lactis is a Gram-positive bacterium that is widely used as a cell factory for the expression of heterologous proteins that are relevant in the pharmaceutical and nutraceutical fields. The signal peptide of the major secreted protein of L. lactis, Usp45, has been employed extensively in engineering strategies to secrete proteins of interest. However, the biological function of Usp45 has remained obscure despite more than 25 years of research. Studies on Usp45 homologs in other Gram-positive bacteria suggest that Usp45 may play a role in cell wall turnover processes. Here, we show the effect of inactivation and overexpression of the usp45 gene on L. lactis growth, phenotype, and cell division. Our results are in agreement with those obtained in streptococci and demonstrate that the L. lactis Usp45 protein is essential for proper cell division. We also show that the usp45 promoter is highly activated by galactose. Overall, our results indicate that Usp45 mediates cell separation, probably by acting as a peptidoglycan hydrolase.

Original languageEnglish
Article numbere00903-20
Pages (from-to)1-14
Number of pages14
JournalApplied and environmental microbiology
Volume86
Issue number16
Early online date12-Jun-2020
DOIs
Publication statusPublished - 1-Aug-2020

Keywords

  • Cell morphology
  • Cell separation
  • Lactococcus lactis
  • Peptidoglycan synthesis
  • Usp45

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