Active lipoprotein precursors in the Gram-positive eubacterium Lactococcus lactis.
Lipid-modified proteins play important roles at the interface between eubacterial cells and their environment. The importance of lipoprotein processing by signal peptidase II (SPase II) is underscored by the fact that this enzyme is essential for viability of the Gram-negative eubacterium Escherichia coli. In contrast, SPase II is not essential for growth and viability of the Gram-positive eubacterium Bacillus subtilis. This could be due to alternative amino-terminal lipoprotein processing, which was shown previously to occur in SPase II mutants of B. subtilis. Alternatively, uncleaved lipoprotein precursors might be functional. To explore further the importance of lipoprotein processing in Gram-positive eubacteria, an SPase II mutant strain of Lactococcus lactis was constructed. Although some of the 39 (predicted) lactococcal lipoproteins, such as PrtM and OppA, are essential for growth in milk, the growth of SPase II mutant L. lactis cells in this medium was not affected. Furthermore, the activity of the strictly PrtM-dependent extracellular protease PrtP, which is required for casein degradation, was not impaired in the absence of SPase II. Importantly, no alternative processing of pre-PrtM and pre-OppA was observed in cells lacking SPase II. Taken together, these findings show for the first time that authentic lipoprotein precursors retain biological activity.
Venema
Roelke
R
Department of Genetics, University of Groningen, Groningen Biomolecular Sciences and Biotechnology Institute, Kerklaan 30, 9751 NN Haren, The Netherlands.
Tjalsma
Harold
H
van Dijl
Jan Maarten
JM
de Jong
Anne
A
Leenhouts
Kees
K
Buist
Girbe
G
Venema
Gerard
G
D016282:Aspartic Acid Endopeptidases / Q000235:genetics / Q000502:physiology; D001426:Bacterial Proteins / Q000096:biosynthesis / Q000502:physiology; D001483:Base Sequence; D002352:Carrier Proteins / Q000096:biosynthesis / Q000502:physiology; D002455:Cell Division; D013294:Lactococcus lactis / Q000737:chemistry* / Q000254:growth & development; D008074:Lipoproteins / Q000096:biosynthesis* / Q000502:physiology; D008565:Membrane Proteins / Q000096:biosynthesis / Q000502:physiology; D008969:Molecular Sequence Data; D011498:Protein Precursors; D011499:Protein Processing, Post-Translational; D021382:Protein Sorting Signals
D001426:Bacterial Proteins; D002352:Carrier Proteins; D008074:Lipoproteins; D008565:Membrane Proteins; D011498:Protein Precursors; D021382:Protein Sorting Signals; C093804:PrtM protein, Lactococcus lactis; C046506:oligopeptide-binding protein, bacteria; D016282:Aspartic Acid Endopeptidases; C095652:signal peptidase II