Table 1

Properties of currents recorded in X. laevis oocytes expressing mutant and WT P2X₁ receptors pEC₅₀ is −log 10 EC₅₀ (molar). Peak I is the current recorded in response to a maximal concentration of ATP. For MTSEA biotinylation, Y indicates MTSEA biotinylation was observed, and N indicates MTSEA biotinylation was not observed. Values are shown ± S.E.

Mutant	EC₅₀	pEC₅₀	Peak I	Half Width	MTSEA Biotinylation
			nA	ms
WT	1.2	5.97 ± 0.07	−6383 ± 504	1847 ± 262	N
C117A	3.2	5.50 ± 0.04^1-160	−7204 ± 784	1912 ± 510	N
C126A	4.6	5.34 ± 0.05^1-160	−5932 ± 480	1156 ± 256	Y
C132A	4.8	5.32 ± 0.01^1-160	−3523 ± 544^1-160	509 ± 47^1-160	Y
C149A	5.1	5.35 ± 0.11^1-160	−5908 ± 908	1044 ± 172^1-150	Y
C159A	2.0	5.74 ± 0.10	−3436 ± 246^1-160	1747 ± 342	Y
C165A	2.7	5.60 ± 0.07^1-160	−6651 ± 756	1701 ± 198	N
C217A	9.8	5.04 ± 0.07^1-160	−6965 ± 412	1825 ± 366	Y
C227A	54.4	4.37 ± 0.16^1-160	−5031 ± 1191	1402 ± 93	Y
C261A	1.4	5.98 ± 0.17	−406 ± 128^1-160	1167 ± 298	N
C270A	2.3	5.67 ± 0.09^1-150	−262 ± 77^1-160	685 ± 40^1-150	N
C117A/C165A	5.9	5.25 ± 0.07^1-160	−5649 ± 742	841 ± 131^1-150	N
C126A/C132A	105.2	4.06 ± 0.18^1-160	−4007 ± 1078^1-150	597 ± 99^1-160	N
C126A/C149A	2.4	5.62 ± 0.03^1-160	−6600 ± 473	859 ± 135^1-150	N
C126A/C159A	4.6	5.35 ± 0.07^1-160	−6440 ± 309	948 ± 112^1-150	N
C132A/C149A	26.5	4.59 ± 0.05^1-160	−6459 ± 498	560 ± 123^1-160	N
C132A/C159A	2.2	5.67 ± 0.03^1-150	−5887 ± 1007	720 ± 166^1-150	N
C149A/C159A	10.3	5.00 ± 0.04^1-160	−7472 ± 410	1066 ± 246	N
C217A/C227A	4.3	5.42 ± 0.12^1-160	−7017 ± 465	1431 ± 31	N
C117A/C126A	NF				N
C117A/C149A	NF				N
C126A/C165A	NF				N
C159A/C165A	NF				N
C149A/C165A	NF				N
C165A/C217A	NF				N

N.F., nonfunctional channel
↵1-150 p < 0.05; different from WT as measured by Student t test.
↵1-160 p < 0.01; different from WT as measured by Student t test.