Murata Takeshi, Yoshikawa Yasushi, Hosaka Toshiaki, Takase Kazuma, Kakinuma Yoshimi, Yamato Ichiro, Kikuchi Takeshi
The Medical Research Council Dunn Human Nutrition Unit, Hills Road, Cambridge CB2 2XY, UK.
J Biochem. 2002 Nov;132(5):789-94. doi: 10.1093/oxfordjournals.jbchem.a003288.
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.
