Figure 6

The ATA-binding site. (a) Propose ATP-binding site of PMCA. All residues identified in PMCA1 are conserved in PMCA4 as follow (PMCA1 → PMCA4): Asp475–Lys476–Thr477 → Asp465–Lys466–Thr467; Thr708–Gly709 → Thr696–Gly697; Lys773 → Lys661; Asp797–Trh799–Asp801 → Asp785–Trh787–Asp789. (b) Propose ATA·Mg-binding site on the PMCA1 structure. All residues identified in PMCA1 are conserved in PMCA4 as follow (PMCA1 → PMCA4): Asp475–Thr477 → Asp465–Thr467; Val707–Thr708–Gly709 → Val695–Thr696–Gly697; SER768–Pro770 → SER756–Pro758. (c) Trp residues of PMCA near ATA·Mg: Trp759 (P-domain) at 20.8 Å, Trp844 (P-domain) at 29.9 Å and Trp664 (N-domain) at 34.5 Å. These residues correspond to Trp 747, Trp 832 and Trp652 in PMCA4. (d) Relative fluorescence of ATA bound to E2, E1Ca, E1(Ca)P and E2P (E2·BeF) states of PMCA. The fluorescence of ATA bound to E2 state was normalized to 1. (e) Binding of ATA·Mg to PMCA·ATP complex. (f) Binding of PMCA·ATP to ATA·Mg complex. Color code: The oxygen, carbon, phosphorus and hydrogen atoms are colored red, blue, orange and white, respectively. The magnesium ion is represented as a green sphere. The ATA molecule is shown in blue light (b) or pink (c,e,f). In (d), the values are the mean ± SE of three independent experiments. *P < 0.01 with respect to E2.