164
Calcium Biochemistry
Actuator
domain
Nucleotide
binding
domain
110
°
80
°
30
°
D601
D703
M5
M2
M1
M9
M10
M7
M1
M3
M6
M8
M7
P1
P2
M4
M6
M5
K684
D703
E183
D351
D601
M9
M10
E771
D800
E309
E109
N111
N114
E905
M4
M2
M6
M2
M1
M4
M8
M3
M4
P2
P1
K684
E243
E109
E300
E908
E771
D796
D800
Ca
2
+
Ca
2
+
Ca
2
+
N114
N111
E183
Carboxy
terminus
Phosphorylation
domain
Amino
terminus
Actuator
domain
ATP
Nucleotide
binding
domain
Cytosol
Membrane
Lumen
E2
(a)
E1Ca
2
(b)
Phosphorylation
domain
Carboxy
terminus
Fig. 5
Structures of the SERCA pump in (a) the Ca
2
+
-free (thapsigargin-bound) form and (b) the Ca
2
+
-bound form. The three cytosolic domains are
indicated as A (actuator), P (phosphorylation), and N (nucleotide binding) domains. The P-domain (with N inserted) connects transmembrane helices
M4 and M5. Within the P-domain, Asp351, which is phosphorylated during the reaction cycle, is also indicated. A number of residues important for the
catalytic center or the Ca
2
+
binding sites within the membrane are shown (Reprinted with permission from Green & MacLennan, 2002,
Nature
418
,
598–599).
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