title: Nucleotide-binding sites in V-type Na+-ATPase from Enterococcus hirae.
abstract: Enterococcus hirae V-ATPase, in contrast to most V-type ATPases, is resistant to N-ethylmaleimide (NEM). Alignment of the amino acid sequences of NtpA suggests that the NEM-sensitive Cys of V-type ATPases is replaced by Ala in E. hirae V-ATPase. Consistent with this prediction, the V-ATPase became sensitive upon substitution of the Ala with Cys. The three-dimensional structure of the NtpB subunit of V-ATPase was modeled based on the structure of the corresponding subunit (alpha subunit) of bovine F(1)-ATPase by homology modeling. Overall, the 3D structure of the subunit resembled that of alpha subunit of bovine F(1)-ATPase. The NtpB subunit, which lacks the P-loop consensus sequence for nucleotide binding, was predicted to bind a nucleotide at the modeled nucleotide-binding site. Experimental data supported the prediction that the E. hirae V-ATPase had about six nucleotide-binding sites.
authors.affiliation: The Medical Research Council Dunn Human Nutrition Unit, Hills Road, Cambridge CB2 2XY, UK.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Murata
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Yoshikawa
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Hosaka
authors.forename: Kazuma
authors.initials: K
authors.lastname: Takase
authors.forename: Yoshimi
authors.initials: Y
authors.lastname: Kakinuma
authors.forename: Ichiro
authors.initials: I
authors.lastname: Yamato
authors.forename: Takeshi
authors.initials: T
authors.lastname: Kikuchi
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D002417:Cattle; D016983:Enterococcus / Q000378:metabolism*; D005033:Ethylmaleimide / Q000494:pharmacology; D008969:Molecular Sequence Data; D006180:Proton-Translocating ATPases / Q000378:metabolism; D012964:Sodium / Q000378:metabolism; D013439:Sulfhydryl Reagents / Q000494:pharmacology; D025262:Vacuolar Proton-Translocating ATPases / Q000378:metabolism*
chemical_list: D013439:Sulfhydryl Reagents; D012964:Sodium; D000251:Adenosine Triphosphatases; D025262:Vacuolar Proton-Translocating ATPases; D006180:Proton-Translocating ATPases; D005033:Ethylmaleimide