Mutation site	Ion	K_{D closed}	K_{D open}	Location	V equivalent^{^a}	References
					mV
High affinity	Ca²⁺
Ca²⁺ bowl		3.5–4.5 μM	0.6–2.0 μM	RCK2?	60–80	Schreiber and Salkoff, 1997; Bian et al., 2001; Braun and Sy, 2001; Bao et al., 2002; Xia et al., 2002
M513		3.5–3.8 μM	0.8–0.9 μM	RCK1	70–80	Bao et al., 2002
D362/D367		17.2 ± 4.0 μM	4.6 ± 1.0 μM	RCK1	60–80	Xia et al., 2002
D81				S0–S1	10–30	Braun and Sy, 2001
Low affinity	Ca²⁺/Mg²⁺			RCK1	∼60
E374/E399	Mg²⁺				60–70	Shi et al., 2002
	Ca²⁺	4.1 ± 3.5 mM	1.8 ± 1.2 mM		50–70	Xia et al., 2002
		2.3–3.1 mM	0.5–0.9 mM		50–70	Zhang et al., 2001
	Mg²⁺	9–22 mM	2–6 mM		70	Zhang et al., 2001
		15 mM	3.6 mM		75	Shi and Cui, 2001
High affinity	Ca²⁺
Δ896–903 + M513I					∼125	Bao et al., 2002
D(897–901)N + D362A/D367A					∼140	Xia et al., 2002
D895N + D81N					∼80	Braun and Sy, 2001

Mutation site	Ion	K_{D closed}	K_{D open}	Location	V equivalent^{^a}	References
					mV
High affinity	Ca²⁺
Ca²⁺ bowl		3.5–4.5 μM	0.6–2.0 μM	RCK2?	60–80	Schreiber and Salkoff, 1997; Bian et al., 2001; Braun and Sy, 2001; Bao et al., 2002; Xia et al., 2002
M513		3.5–3.8 μM	0.8–0.9 μM	RCK1	70–80	Bao et al., 2002
D362/D367		17.2 ± 4.0 μM	4.6 ± 1.0 μM	RCK1	60–80	Xia et al., 2002
D81				S0–S1	10–30	Braun and Sy, 2001
Low affinity	Ca²⁺/Mg²⁺			RCK1	∼60
E374/E399	Mg²⁺				60–70	Shi et al., 2002
	Ca²⁺	4.1 ± 3.5 mM	1.8 ± 1.2 mM		50–70	Xia et al., 2002
		2.3–3.1 mM	0.5–0.9 mM		50–70	Zhang et al., 2001
	Mg²⁺	9–22 mM	2–6 mM		70	Zhang et al., 2001
		15 mM	3.6 mM		75	Shi and Cui, 2001
High affinity	Ca²⁺
Δ896–903 + M513I					∼125	Bao et al., 2002
D(897–901)N + D362A/D367A					∼140	Xia et al., 2002
D895N + D81N					∼80	Braun and Sy, 2001

V equivalent is the shift required in the voltage to maintain the same Po of 0.5 after the indicated mutations in the presence of 10–100 μM Ca²⁺_i for the high affinity sites and 10 mM Ca²⁺_i or Mg²⁺_i for the low affinity sites.

All sequence numbers are adjusted to the sequence with EMBL/GenBank/DDBJ accession no. L16912 (Butler et al., 1993) from Nucleotide in PubMed with the numbering starting at the second M (MDALI). The mutations that identify each site and identifying sequence are: The Ca²⁺ bowl is defined by Sequence I in the text. Various mutations in this region that greatly reduce Ca²⁺ sensitivity typically include one or more of the five consecutive aspartates (D897–901), such as D(897–901)N or D897–898 deleted, or the D895N which changes the D two residues before the string of aspartates. M513I identified by MRSFIK. D362A/D367A identified by DFLHKD. D81N identified by DEKEE. E399A identified by EFYQG.

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