7wem
From Proteopedia
Solid-state NMR Structure of TFo c-Subunit Ring
Structural highlights
Function[ATPL_BACP3] F(1)F(0) ATP synthase produces ATP from ADP in the presence of a proton or sodium gradient. F-type ATPases consist of two structural domains, F(1) containing the extramembraneous catalytic core and F(0) containing the membrane proton channel, linked together by a central stalk and a peripheral stalk. During catalysis, ATP synthesis in the catalytic domain of F(1) is coupled via a rotary mechanism of the central stalk subunits to proton translocation.[HAMAP-Rule:MF_01396] Key component of the F(0) channel; it plays a direct role in translocation across the membrane. A homomeric c-ring of 10 subunits forms the central stalk rotor element with the F(1) delta and epsilon subunits.[HAMAP-Rule:MF_01396] Publication Abstract from PubMedProton translocation through the membrane-embedded Fo component of F-type ATP synthase (FoF1) is facilitated by the rotation of the Fo c-subunit ring (c-ring), carrying protons at essential acidic amino acid residues. Cryo-electron microscopy (Cryo-EM) structures of FoF1 suggest a unique proton translocation mechanism. To elucidate it based on the chemical conformation of the essential acidic residues of the c-ring in FoF1, we determined the structure of the isolated thermophilic Bacillus Fo (tFo) c-ring, consisting of 10 subunits, in membranes by solid-state NMR. This structure contains a distinct proton-locking conformation, wherein Asn23 (cN23) C(gamma)O and Glu56 (cE56) C(delta)OH form a hydrogen bond in a closed form. We introduced stereo-array-isotope-labeled (SAIL) Glu and Asn into the tFoc-ring to clarify the chemical conformation of these residues in tFoF1-ATP synthase (tFoF1). Two well-separated (13)C signals could be detected for cN23 and cE56 in a 505 kDa membrane protein complex, respectively, thereby suggesting the presence of two distinct chemical conformations. Based on the signal intensity and structure of the tFoc-ring and tFoF1, six pairs of cN23 and cE56 surrounded by membrane lipids take the closed form, whereas the other four in the a-c interface employ the deprotonated open form at a proportion of 87%. This indicates that the a-c interface is highly hydrophilic. The pKa values of the four cE56 residues in the a-c interface were estimated from the cN23 signal intensity in the open and closed forms and distribution of polar residues around each cE56. The results favor a rotation of the c-ring for ATP synthesis. Chemical Conformation of the Essential Glutamate Site of the c-Ring within Thermophilic Bacillus FoF1-ATP Synthase Determined by Solid-State NMR Based on its Isolated c-Ring Structure.,Todokoro Y, Kang SJ, Suzuki T, Ikegami T, Kainosho M, Yoshida M, Fujiwara T, Akutsu H J Am Chem Soc. 2022 Jul 29. doi: 10.1021/jacs.2c03580. PMID:35905443[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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