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Applied and Environmental Microbiology, September 2001, p. 4119-4127, Vol. 67, No. 9
Laboratoire de Génétique
Appliquée, Unité de Recherches Laitières et de
Génétique Appliquée, Institut National de la
Recherche Agronomique, Domaine de Vilvert, 78352 Jouy en Josas Cedex,
France
Received 8 June 2001/Accepted 22 June 2001
Lactic acid bacteria are food-grade microorganisms that are
potentially good candidates for production of heterologous proteins of
therapeutical or technological interest. We developed a model for
heterologous protein secretion in Lactococcus lactis using the staphylococcal nuclease (Nuc). The effects on protein secretion of
alterations in either (i) signal peptide or (ii) propeptide sequences
were examined. (i) Replacement of the native Nuc signal peptide
(SPNuc) by that of L. lactis protein Usp45
(SPUsp) resulted in greatly improved secretion efficiency
(SE). Pulse-chase experiments showed that Nuc secretion kinetics was
better when directed by SPUsp than when directed by
SPNuc. This SPUsp effect on Nuc secretion is
not due to a better antifolding activity, since SPUsp:Nuc
precursor proteins display enzymatic activity in vitro, while
SPNuc:Nuc precursor proteins do not. (ii) Deletion of the
native Nuc propeptide dramatically reduces Nuc SE, regardless of which
SP is used. We previously reported that a synthetic propeptide,
LEISSTCDA, could efficiently replace the native Nuc propeptide to
promote heterologous protein secretion in L. lactis (Y. Le
Loir, A. Gruss, S. D. Ehrlich, and P. Langella, J. Bacteriol.
180:1895-1903, 1998). To determine whether the LEISSTCDA effect is due
to its acidic residues, specific substitutions were introduced,
resulting in neutral or basic propeptides. Effects of these two new
propeptides and of a different acidic synthetic propeptide were tested.
Acidic and neutral propeptides were equally effective in enhancing Nuc
SE and also increased Nuc yields. In contrast, the basic propeptide
strongly reduced both SE and the quantity of secreted Nuc. We have
shown that the combination of the native SPUsp and a
neutral or acidic synthetic propeptide leads to a significant
improvement in SE and in the quantity of synthesized Nuc. These
observations will be valuable in the production of heterologous
proteins in L. lactis.
0099-2240/01/$04.00+0 DOI: 10.1128/AEM.67.9.4119-4127.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Signal Peptide and Propeptide Optimization for
Heterologous Protein Secretion in Lactococcus
lactis
*
Corresponding author. Mailing address: Laboratoire de
Génétique Appliquée, Unité de Recherches
Laitières et de Génétique Appliquée, Institut
National de la Recherche Agronomique, Domaine de Vilvert, 78352 Jouy en
Josas Cedex, France. Phone: 33 01 34 65 20 83. Fax: 33 01 34 65 20 65. E-mail: langella{at}jouy.inra.fr.
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