A 100 kDa vanadate and lanzoprazole-sensitive ATPase from Streptococcus mutans membrane Prislaine P. Magalha ˜es a , Tony P. Paulino a , Geraldo Thedei Jr. b , Roy E. Larson c , Pietro Ciancaglini a, * a Departamento de Qu½ ´mica, Faculdade de Filosofia Cie ˆncias e Letras de Ribeira˜o Preto (FFCLRP), Universidade de Sa˜o Paulo (USP), 14040-901 Ribeira ˜o Preto, SP, Brazil b Instituto de Cie ˆncias Biolo ´gicas e da Sau ´de, Universidade de Uberaba, Uberaba, MG, Brazil c Departamento de Biologia Celular e Molecular e Bioagentes Patoge ˆnicos, Faculdade de Medicina de Ribeira ˜o Preto (FMRP), Universidade de Sa˜o Paulo (USP), Ribeira˜o Preto, SP, Brazil Accepted 16 June 2003 Introduction It is known that Streptococcus mutans comprises a substantial part of the cell count in dental plaques subject to caries development, and its importance in dental caries aetiology is unquestionable. 1 The cariogenic potential of these bacteria is due to the production of organic acids derived from the meta- bolism of sucrose, fructose and glucose, among other sugars. Amongst the acids formed, lactic and acetic acid account for more than 95% of the total anions produced by S. mutans and Streptococ- cus sobrinus. 2 The acid generation capacity (acidogeny) implies the necessity of mechanisms for these organisms to tolerate an acidic environment (acidurance). It is known that this behaviour depends, at least in part, on the ATPases located in the plasma membrane. These enzymes are responsible for cytoplasmic pro- ton extrusion. 3—8 The F 1 F o -ATPase of Streptococcus faecalis, described as the main enzyme responsible for this translocation activity, was purified. 9 In Archives of Oral Biology (2003) 48, 815—824 KEYWORDS Streptococcus mutans; H þ -ATPase; P-type ATPase; Vanadate; Lanzoprazole; Phosphoenzyme Summary The cariogenic potential of Streptococcus mutans is due to the production of organic acids derived from energy metabolism, which implies the need of mechan- isms for the organism to tolerate this acidic environment. The F 1 F o -ATPase is generally considered as the main enzyme responsible for cytoplasmic proton extrusion, but mutations that resulted in a 50% reduction in F 1 F o -ATPase activity in S. mutans still allowed the micro-organism to grow and extrude acid, keeping the intracellular pH one pH unit above the extracellular ambient. This finding suggests the existence of other enzymatic (or cellular) mechanisms that keep the cytosolic pH neutral during micro- organism growth. This paper describes a membrane protein in S. mutans, with a molecular weight of 100 kDa, which exhibits ATPase activity inhibited by classic inhibitors of P-type ATPases (orthovanadate) and H þ ,K þ -ATPase (lanzoprazole), has an optimum pH comparable to other H þ -ATPases and undergoes phosphorylation during the catalytic reaction, like that of H þ -ATPases described in yeast and plant plasma membrane. Together, these results strongly suggest that the enzyme we describe here is a P-type H þ -ATPase or H þ ,ion-ATPase that can act in association with F 1 F o -ATPase during the growth of the S. mutans. ß 2003 Elsevier Ltd. All rights reserved. * Corresponding author. Tel.: þ55-16-602-3753; fax: þ55-16-633-8151. E-mail address: pietro@ffclrp.usp.br (P. Ciancaglini). 0003–9969/$ — see front matter ß 2003 Elsevier Ltd. All rights reserved. doi:10.1016/S0003-9969(03)00177-8