Cryo-EM structure of the Blastochloris viridis LH1–RC complex at 2.9 Å

DOI: 10.1038/s41586-018-0014-5

Authors: Pu Qian (University of Sheffield) , C. Alistair Siebert (Diamond Light Source) , Peiyi Wang (University of Leeds) , Daniel P. Canniffe (University of Sheffield) , C. Neil Hunter (University of Sheffield)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Nature , VOL 103

State: Published (Approved)
Published: April 2018
Diamond Proposal Number(s): 13888

Abstract: The light-harvesting 1-reaction centre (LH1-RC) complex is a key functional component of bacterial photosynthesis. Here we present a 2.9 Å resolution cryo-electron microscopy structure of the bacteriochlorophyll b-based LH1-RC complex from Blastochloris viridis that reveals the structural basis for absorption of infrared light and the molecular mechanism of quinone migration across the LH1 complex. The triple-ring LH1 complex comprises a circular array of 17 β-polypeptides sandwiched between 17 α- and 16 γ-polypeptides. Tight packing of the γ-apoproteins between β-polypeptides collectively interlocks and stabilizes the LH1 structure; this, together with the short Mg-Mg distances of bacteriochlorophyll b pairs, contributes to the large redshift of bacteriochlorophyll b absorption. The 'missing' 17th γ-polypeptide creates a pore in the LH1 ring, and an adjacent binding pocket provides a folding template for a quinone, Q P, which adopts a compact, export-ready conformation before passage through the pore and eventual diffusion to the cytochrome bc 1 complex.

Journal Keywords: Antenna complex; Cryoelectron microscopy

Subject Areas: Biology and Bio-materials

Diamond Offline Facilities: Electron Bio-Imaging Centre (eBIC)
Instruments: Krios I-Titan Krios I at Diamond

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