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Structural characterization of the transmembrane domain from subunit e of yeast F1Fo-ATP synthase: a helical GXXXG motif located just under the micelle surface. Biochemistry 2008 Feb 19;47(7):1910-7

Date

01/29/2008

Pubmed ID

18220416

DOI

10.1021/bi7015475

Abstract

F1Fo-ATP synthase is a large multiprotein complex, including at least 10 subunits in the membrane-bound Fo-sector. One of these Fo proteins is subunit e (Su e), involved in the stable dimerization of F1Fo-ATP synthase, and required for the establishment of normal cristae membrane architecture. As a step toward enabling structure-function studies of the Fo-sector, the Su e transmembrane region was structurally characterized in micelles. Based on a series of NMR and CD (circular dichroism) studies, a structural model of the Su e/micelle complex was constructed, indicating Su e is largely helical, and emerges from the micelle with Arg20 near the phosphate head groups. Su e only adopts this folded conformation in the context of the micelle, and is essentially disordered in DMSO, water or trifluoroethanol/water. Within the micelle the C-terminal Ala10-Arg20 stretch is helical, while the region N-terminal may be transiently helical, based on negative CSI (chemical shift index) values. The Ala10-Arg20 helix contains the G14XXXG18 motif, which has been proposed to play an important role in dimer formation with another protein from the Fo-sector. The Gly on the C-terminal end of this motif (Gly18) is slightly more mobile than the more buried Gly14, based on NMR order parameter measurements (Gly14 S2 = 0.950; Gly18 S2 = 0.895). Only one Su e transmembrane peptide is bound per micelle, and micelles are 22-23 A in diameter, composed of 51 +/- 4 dodecylphosphocholine detergent molecules. Although there is no evidence for Su e homodimerization via the transmembrane domain, potentially synergistic roles for N-terminal (membrane) and C-terminal (soluble) domain interactions may still occur. Furthermore, the presence of a buried charged residue (Arg7) suggests there may be interactions with other Fo-sector protein(s) that stabilize this charge, and possibly drive the folding of the N-terminal 9 residues of the transmembrane domain.

Author List

Yao H, Stuart RA, Cai S, Sem DS

Author

Rosemary Stuart PhD Professor in the Biology department at Marquette University




MESH terms used to index this publication - Major topics in bold

Amino Acid Sequence
Micelles
Molecular Sequence Data
Protein Conformation
Proton-Translocating ATPases
Saccharomyces cerevisiae
jenkins-FCD Prod-482 91ad8a360b6da540234915ea01ff80e38bfdb40a