title: A unique F-type H⁺-ATPase from Streptococcus mutans: an active H⁺ pump at acidic pH.
abstract: We have shown previously that the Streptococcus mutans F-type H(+)-ATPase (F(O)F(1)) c subunit gene could complement Escherichia coli defective in the corresponding gene, particularly at acidic pH (Araki et al., (2013) [14]). In this study, the entire S. mutans F(O)F(1) was functionally assembled in the E. coli plasma membrane (SF(O)F(1)). Membrane SF(O)F(1) ATPase showed optimum activity at pH 7, essentially the same as that of the S. mutans, although the activity of E. coli F(O)F(1) (EF(O)F(1)) was optimum at pH≥9. The membranes showed detectable ATP-dependent H(+)-translocation at pH 5.5-6.5, but not at neutral conditions (pH≥7), consistent with the role of S. mutans F(O)F(1) to pump H(+) out of the acidic cytoplasm. A hybrid F(O)F(1), consisting of membrane-integrated F(O) and -peripheral F(1) sectors from S. mutans and E. coli (SF(O)EF(1)), respectively, essentially showed the same pH profile as that of EF(O)F(1) ATPase. However, ATP-driven H(+)-transport was similar to that by SF(O)F(1), with activity at acidic pH. Replacement of the conserved c subunit Glu53 in SF(O)F(1) abolished H(+)-transport at pH 6 or 7, suggesting its role in H(+) transport. Mutations in the SF(O)F(1) c subunit, Ser17Ala or Glu20Ile, changed the pH dependency of H(+)-transport, and the F(O) could transport H(+) at pH 7, as the membranes with EF(O)F(1). Ser17, Glu20, and their vicinity were suggested to be involved in H(+)-transport in S. mutans at acidic pH.
authors: Department of Bioscience, Nagahama Institute of Bioscience and Technology, 1266 Tamura, Nagahama, Shiga 526-0829, Japan.
authors: Yuka
authors: Y
authors: Sasaki
authors: Department of Bioscience, Nagahama Institute of Bioscience and Technology, 1266 Tamura, Nagahama, Shiga 526-0829, Japan.
authors: Eri
authors: E
authors: Nogami
authors: Department of Molecular Biology, School of Pharmacy, Iwate Medical University, 2-1-1 Nishitokuta, Yahaba, Iwate 028-3694, Japan.
authors: Masatomo
authors: M
authors: Maeda
authors: Department of Molecular Biology, School of Pharmacy, Iwate Medical University, 2-1-1 Nishitokuta, Yahaba, Iwate 028-3694, Japan.
authors: Mayumi
authors: M
authors: Nakanishi-Matsui
authors: Department of Bioscience, Nagahama Institute of Bioscience and Technology, 1266 Tamura, Nagahama, Shiga 526-0829, Japan. Electronic address: a_iwamoto@nagahama-i-bio.ac.jp.
authors: Atsuko
authors: A
authors: Iwamoto-Kihara
mesh_terms: D002462:Cell Membrane / Q000737:chemistry* / Q000201:enzymology*; D004789:Enzyme Activation; D004795:Enzyme Stability; D006863:Hydrogen-Ion Concentration; D006180:Proton-Translocating ATPases / Q000737:chemistry* / Q000378:metabolism*; D013295:Streptococcus mutans / Q000201:enzymology*; D013379:Substrate Specificity
chemical_list: D006180:Proton-Translocating ATPases
keywords: ATP synthase; Dental caries; E. coli F(O)F(1) expressed in E. coli membranes; EF(O)F(1); F(O)F(1); H(+)-ATPase; S. mutans; S. mutans F(O)F(1) expressed in E. coli membranes; SF(O)EF(1); SF(O)F(1); c Subunit; hybrid F(O)F(1) formed from S. mutans F(O) and E. coli F(1)