Figure 4.
Fig. 4. Part of the RC structure near the secondary
quinone, Q[B] binding site, as determined for the Q[B]^ state
by Stowell et al. (18). Possible proton transfer pathways
(P1-P3) proposed by Abresch et al. (19) are shown by dashed
lines. One carbonyl oxygen of Q[B] is located near Ser-L223 and
the backbone NH of Ile-L224 (not shown); the other carbonyl
oxygen of Q[B] is located near His-L190. Nearby are two
carboxylic acid groups Asp-L213 and Glu-L212 that have been
implicated in proton transfer to reduced Q[B] (reactions 2a and
2b, respectively) (8-13) and to which the proton transfer
pathways lead. Also shown are a His cluster (consisting of H68,
H126, and H128) and a carboxylic acid cluster (consisting of
Asp-L213, Asp-L210, Asp-M17, Glu-H173, Asp-H170, and Asp-M124).
state
by Stowell et al. (18). Possible proton transfer pathways
(P1-P3) proposed by Abresch et al. (19) are shown by dashed
lines. One carbonyl oxygen of Q[B] is located near Ser-L223 and
the backbone NH of Ile-L224 (not shown); the other carbonyl
oxygen of Q[B] is located near His-L190. Nearby are two
carboxylic acid groups Asp-L213 and Glu-L212 that have been
implicated in proton transfer to reduced Q[B] (reactions 2a and
2b, respectively) (8-13) and to which the proton transfer
pathways lead. Also shown are a His cluster (consisting of H68,
H126, and H128) and a carboxylic acid cluster (consisting of
Asp-L213, Asp-L210, Asp-M17, Glu-H173, Asp-H170, and Asp-M124).