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. 2021 Oct 21;478(20):3775–3790. doi: 10.1042/BCJ20210631

Figure 4. The bacteriochlorophylls and RC cofactors.

Figure 4.

Proteins and carotenoids are omitted for clarity. (A) View from the periplasmic side of the membrane showing the incomplete ring of 28 BChls, coloured in two shades of green to distinguish between pairs belonging to individual LH1 αβ subunits. Mg–Mg distances in Ångstroms for intra- and inter-subunit BChls are shown, and also for the nearest and furthest approach of BChls to the RC special pair of BChls (red). RC accessory BChls are in orange and bacteriopheophytins are in blue. (B) Two adjacent pairs of LH1 BChls viewed from the periplasmic side with the BChls in spacefill representation (upper image) to emphasise the close contacts between these pigments, and as stick models (lower image) to show the coordination by histidine residues from the LH1 α (yellow) and β (blue) polypeptides. (C) View in the plane of the membrane of two adjacent BChl pairs, coloured as in (A). Overlaps between the rings of the BChl macrocycle are shown. (D) A single LH1 subunit (αβ8) showing coordination by histidine residues and hydrogen bonds from C-terminal Trp residues to C3 acetyl carbonyls of the BChls.