Overall structures of the RC from Tch. tepidum.
(a) The ribbon models represent four polypeptide chains:
Cyt (red), L (green), M (blue), and H (yellow). The dotted circles
indicate two regions where the loop conformations are different from
those of the Blc. viridis RC (Left:
Gln-C161–Asn-C162; Right: Gly-L56–Leu-L64).
(b) The ball-and-stick models represent the
configuration of the prosthetic groups (DA and
DB: special-pair; BChA and BChB:
bacteriochlorophyll a monomers; BPhA and
BPhB: bacteriopheophytin a molecules;
QA: menaquinone-8; Fe: nonheme iron; Spx: spirilloxanthin;
Heme-1, -2, -3, and -4: heme c groups). The secondary
quinone (QB) site (blue dotted circle) is empty because
QB was not observed in the electron density maps.
(c) The space-filling models represent the detergent and
lipid molecules observed on the molecular surface. Six β-OG molecules
are represented by cyan. One LDAO molecule and one lipid molecule (P)
are represented by green and magenta, respectively. The dotted circle
indicates the binding site of the cardiolipin in the Rb.
sphaeroides RC structure (49).