Environmental Engineering Reference
In-Depth Information
Fig. 5
Overall structure of PSII dimer from
Thermosynechococcus vulcanus
at a resolution of
1.9Å. View from the direction perpendicular to the membrane normal.
a
Overall structure. The
protein subunits are coloured individually in the right hand monomer and in light
grey
in the left-
hand monomer, and the cofactors are coloured in the left-hand monomer and in light
grey
in the
right-hand monomer. Orange balls represent water molecules.
b
Arrangement of water molecules
in the PSII dimer. The protein subunits are coloured in light
grey
and all other cofactors are omit-
ted. The central broken lines are the noncrystallographic two-fold axes relating the two mono-
mers.
Data source
Umena et al. (
2011
)
(one of which is in the Mn
4
Ca cluster), three Cl
−
ions (two of which are near
the Mn
4
CaO
5
cluster), one bicarbonate ion and more than 15 detergents (Fig.
5
)
(Krauß
2003
; Nilsson Lill
2011
; Umena et al.
2011
; Zouni et al.
2001
; Kamiya and
Shen
2003
; Ferreira et al.
2004
; Loll et al.
2005
; Murray et al.
2008
; Kawakami
et al.
2009
; Guskov et al.
2009
; Biesiadka et al.
2004
). PSII reaction center or pri-
mary donor P680 in PSII is an approximately C
2
-symmetric structure formed by
polypeptides (D1 and D2) and six chlorin cofactors: four chlorophyll
a
and two
pheophytin
a
(Pheo
D1
and Pheo
D2
) (Fig.
5
) (Nilsson Lill
2011
; Umena et al.
2011
).
Each PSII monomer consists of more than 1,300 water molecules, yielding a total
of 2,795 water molecules in the dimer (Umena et al.
2011
). The water molecules
are organized into two layers located on the surfaces of the stromal and lumenal
sides, respectively, with the latter having more water molecules than the former
(Umena et al.
2011
). A few water molecules are detected within the membrane
region, most of them serving as ligands to chlorophylls (Umena et al.
2011
).
