title: A 16 kDa protein family overexpressed by Streptococcus thermophilus PB18 in acid environments.
abstract: The one- and two-dimensional protein patterns of Streptococcus thermophilus PB18 in the exponential and stationary phases of growth were analysed. One-dimensional SDS-PAGE showed that a 16 kDa protein was overexpressed in stationary phase as well as 2 h after an acid shock, and that it was not expressed when the bacteria reached the stationary phase in medium with limiting lactose concentrations (5 or 10 g l-1), in which the pH (5.5) was not as acid as in control cultures (pH 4.7, lactose 20 g l-1). The results support the idea that this protein is expressed in response to the acidic environment and not in response to the growth phase. Two-dimensional PAGE showed that nine proteins were expressed only during the exponential phase and ten others only during the stationary phase. The 16 kDa band seen in one-dimensional SDS-PAGE corresponded to a 16 kDa protein family observed on two-dimensional SDS-PAGE/IEF gels, whose expression was increased 8.5-fold when the extracellular pH reached a critical value below 5.0. The N-terminal sequences of proteins from two spots on the two-dimensional gels (members of the 16 kDa family) were determined and found to be identical. The physiological role of this protein family has not yet been elucidated.
authors.affiliation: Departamento de Ciencias de la Salud, Universidad Autónoma Metropolitana - Iztapalapa, 09340 Mexico, DF, Mexico.|Laboratoire des Biosciences de l'Aliment, Unité Associée à I'INRA, Université Henri Poincaré, Nancy 1, BP 239, 54506 Vandoeuvre-lès-Nancy Cedex, France.
authors.forename: Humberto
authors.initials: H
authors.lastname: González-Márquez
authors.affiliation: Laboratoire des Biosciences de l'Aliment, Unité Associée à I'INRA, Université Henri Poincaré, Nancy 1, BP 239, 54506 Vandoeuvre-lès-Nancy Cedex, France.
authors.forename: Clarisse
authors.initials: C
authors.lastname: Perrin
authors.affiliation: Laboratoire des Biosciences de l'Aliment, Unité Associée à I'INRA, Université Henri Poincaré, Nancy 1, BP 239, 54506 Vandoeuvre-lès-Nancy Cedex, France.
authors.forename: Patrice
authors.initials: P
authors.lastname: Bracquart
authors.affiliation: Laboratoire des Biosciences de l'Aliment, Unité Associée à I'INRA, Université Henri Poincaré, Nancy 1, BP 239, 54506 Vandoeuvre-lès-Nancy Cedex, France.
authors.forename: Christiane
authors.initials: C
authors.lastname: Guimont
authors.affiliation: Laboratoire des Biosciences de l'Aliment, Unité Associée à I'INRA, Université Henri Poincaré, Nancy 1, BP 239, 54506 Vandoeuvre-lès-Nancy Cedex, France.
authors.forename: Guy
authors.initials: G
authors.lastname: Linden
mesh_terms: D019342:Acetic Acid / Q000494:pharmacology*; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000096:biosynthesis* / Q000235:genetics; D004591:Electrophoresis, Polyacrylamide Gel; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects*; D006863:Hydrogen-Ion Concentration; D019344:Lactic Acid / Q000494:pharmacology*; D007785:Lactose / Q000378:metabolism; D008969:Molecular Sequence Data; D008970:Molecular Weight; D013291:Streptococcus / Q000235:genetics / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D019344:Lactic Acid; D007785:Lactose; D019342:Acetic Acid