Direct assignment of 13C solid-state NMR signals of TFoF1 ATP synthase subunit c-ring in lipid membranes and its implication for the ring structure.
Direct assignment of 13C solid-state NMR signals of TFoF1 ATP synthase subunit c-ring in lipid membranes and its implication for the ring structure.
J Biomol NMR. 2017 Dec 02;:
Authors: Kang SJ, Todokoro Y, Bak S, Suzuki T, Yoshida M, Fujiwara T, Akutsu H
Abstract
FoF1-ATP synthase catalyzes ATP hydrolysis/synthesis coupled with a transmembrane H+ translocation in membranes. The Fo c-subunit ring plays a major role in this reaction. We have developed an assignment strategy for solid-state 13C NMR (ssNMR) signals of the Fo c-subunit ring of thermophilic Bacillus PS3 (TFo c-ring, 72 residues), carrying one of the basic folds of membrane proteins. In a ssNMR spectrum of uniformly 13C-labeled sample, the signal overlap has been a major bottleneck because most amino acid residues are hydrophobic. To overcome signal overlapping, we developed a method designated as COmplementary Sequential assignment with MInimum Labeling Ensemble (COSMILE). According to this method, we generated three kinds of reverse-labeled samples to suppress signal overlapping. To assign the carbon signals sequentially, two-dimensional C?(i+1)-C'C?(i) correlation and dipolar assisted rotational resonance (DARR) experiments were performed under magic-angle sample spinning. On the basis of inter- and intra-residue 13C-13C chemical shift correlations, 97% of C?, 97% of C? and 92% of C' signals were assigned directly from the spectra. Secondary structure analysis predicted a hairpin fold of two helices with a central loop. The effects of saturated and unsaturated phosphatidylcholines on TFo c-ring structure were examined. The DARR spectra at 15*ms mixing time are essentially similar to each other in saturated and unsaturated lipid membranes, suggesting that TFo c-rings have similar structures under the different environments. The spectrum of the sample in saturated lipid membranes showed better resolution and structural stability in the gel state. The C-terminal helix was suggested to locate in the outer layer of the c-ring.
PMID: 29197977 [PubMed - as supplied by publisher]
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