In:
Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 96, No. 14 ( 1999-07-06), p. 7785-7790
Abstract:
The structure of the subunit c oligomer of the H + -transporting ATP synthase of Escherichia coli has been modeled by molecular dynamics and energy minimization calculations from the solution structure of monomeric subunit c and 21 intersubunit distance constraints derived from cross-linking of subunits. Subunit c folds in a hairpin-like structure with two transmembrane helices. In the c 12 oligomer model, the subunits pack to form a compact hollow cylinder with an outer diameter of 55–60 Å and an inner space with a minimal diameter of 11–12 Å. Phospholipids are presumed to pack in the inner space in the native membrane. The transmembrane helices pack in two concentric rings with helix 1 inside and helix 2 outside. The calculations strongly favor this structure versus a model with helix 2 inside and helix 1 outside. Asp-61, the H + -transporting residue, packs toward the center of the four transmembrane helices of two interacting subunits. From this position at the front face of one subunit, the Asp-61 carboxylate lies proximal to side chains of Ala-24, Ile-28, and Ala-62, projecting from the back face of a second subunit. These interactions were predicted from previous mutational analyses. The packing supports the suggestion that a c–c dimer is the functional unit. The positioning of the Asp-61 carboxyl in the center of the interacting transmembrane helices, rather than at the periphery of the cylinder, has important implications regarding possible mechanisms of H + -transport-driven rotation of the c oligomer during ATP synthesis.
Type of Medium:
Online Resource
ISSN:
0027-8424
,
1091-6490
DOI:
10.1073/pnas.96.14.7785
Language:
English
Publisher:
Proceedings of the National Academy of Sciences
Publication Date:
1999
detail.hit.zdb_id:
209104-5
detail.hit.zdb_id:
1461794-8
SSG:
11
SSG:
12
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