Structure analysis of membrane-reconstituted subunit c-ring of E. coli H+-ATP synthas
 

Abstract The subunit c-ring of H+-ATP synthase (Fo c-ring) plays an essential role in the proton translocation across a membrane driven by the electrochemical potential. To understand its structure and function, we have carried out solid-state NMR analysis under magic-angle sample spinning. The uniformly [13C, 15N]-labeled Fo c from E. coli (EFo c) was reconstituted into lipid membranes as oligomers. Its high resolution two- and three-dimensional spectra were obtained, and the 13C and 15N signals were assigned. The obtained chemical shifts suggested that EFo c takes on a hairpin-type helix-loop-helix structure in membranes as in an organic solution. The results on the magnetization transfer between the EFo c and deuterated lipids indicated that Ile55, Ala62, Gly69 and F76 were lined up on the outer surface of the oligomer. This is in good agreement with the cross-linking results previously reported by Fillingame and his colleagues. This agreement reveals that the reconstituted EFo c oligomer takes on a ring structure similar to the intact one in vivo. On the other hand, analysis of the 13C nuclei distance of [3-13C]Ala24 and [4-13C]Asp61 in the Fo c-ring did not agree with the model structures proposed for the EFo c-decamer and dodecamer. Interestingly, the carboxyl group of the essential Asp61 in the membrane-embedded EFo c-ring turned out to be protonated as COOH even at neutral pH. The hydrophobic surface of the EFo c-ring carries relatively short side chains in its central region, which may allow soft and smooth interactions with the hydrocarbon chains of lipids in the liquid-crystalline state.

• Content Type Journal Article
• DOI 10.1007/s10858-010-9432-x
• Authors
  • Yasuto Todokoro, Osaka University Institute for Protein Research 3-2 Yamadaoka Suita 565-0871 Japan
  • Masatoshi Kobayashi, Osaka University Institute for Protein Research 3-2 Yamadaoka Suita 565-0871 Japan
  • Takeshi Sato, Osaka University Institute for Protein Research 3-2 Yamadaoka Suita 565-0871 Japan
  • Toru Kawakami, Osaka University Institute for Protein Research 3-2 Yamadaoka Suita 565-0871 Japan
  • Ikuko Yumen, Osaka University Institute for Protein Research 3-2 Yamadaoka Suita 565-0871 Japan
  • Saburo Aimoto, Osaka University Institute for Protein Research 3-2 Yamadaoka Suita 565-0871 Japan
  • Toshimichi Fujiwara, Osaka University Institute for Protein Research 3-2 Yamadaoka Suita 565-0871 Japan
  • Hideo Akutsu, Osaka University Institute for Protein Research 3-2 Yamadaoka Suita 565-0871 Japan

• • Journal Journal of Biomolecular NMR
  • Online ISSN 1573-5001
  • Print ISSN 0925-2738

Source: Journal of Biomolecular NMR