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Applied and Environmental Microbiology, November 2000, p. 4772-4778, Vol. 66, No. 11
0099-2240/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.

Streptococcus thermophilus Cell Wall-Anchored Proteinase: Release, Purification, and Biochemical and Genetic Characterization

María Dolores Fernandez-Espla,dagger Peggy Garault, Véronique Monnet, and Françoise Rul*

Unité de Recherche de Biochimie et Structure des Protéines, Institut National de la Recherche Agronomique, 78352 Jouy-en-Josas Cedex, France

Received 12 May 2000/Accepted 4 August 2000

Streptococcus thermophilus CNRZ 385 expresses a cell envelope proteinase (PrtS), which is characterized in the present work, both at the biochemical and genetic levels. Since PrtS is resistant to most classical methods of extraction from the cell envelopes, we developed a three-step process based on loosening of the cell wall by cultivation of the cells in the presence of glycine (20 mM), mechanical disruption (with alumina powder), and enzymatic treatment (lysozyme). The pure enzyme is a serine proteinase highly activated by Ca2+ ions. Its activity was optimal at 37°C and pH 7.5 with acetyl-Ala-Ala-Pro-Phe-paranitroanilide as substrate. The study of the hydrolysis of the chromogenic and casein substrates indicated that PrtS presented an intermediate specificity between the most divergent types of cell envelope proteinases from lactococci, known as the PI and PIII types. This result was confirmed by the sequence determination of the regions involved in substrate specificity, which were a mix between those of PI and PIII types, and also had unique residues. Sequence analysis of the PrtS encoding gene revealed that PrtS is a member of the subtilase family. It is a multidomain protein which is maturated and tightly anchored to the cell wall via a mechanism involving an LPXTG motif. PrtS bears similarities to cell envelope proteinases from pyogenic streptococci (C5a peptidase and cell surface proteinase) and lactic acid bacteria (PrtP, PrtH, and PrtB). The highest homologies were found with streptococcal proteinases which lack, as PrtS, one domain (the B domain) present in cell envelope proteinases from all other lactic acid bacteria.

* Corresponding author. Mailing address: Unité de Recherche de Biochimie et Structure des Protéines, Institut National de la Recherche Agronomique, 78352 Jouy-en-Josas Cedex, France. Phone: (33) 1 34 65 21 49. Fax: (33) 1 34 65 21 63. E-mail: rul{at}jouy.inra.fr.

dagger Present address: Instituto del Frío (CSIC), Departamento de Cienca y Tecnología de Productos Lácteos, Ciudad Universitaria, 28040 Madrid, Spain.

Applied and Environmental Microbiology, November 2000, p. 4772-4778, Vol. 66, No. 11
0099-2240/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.


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