Table 4

SI proteins share high affinity for inhibitors of postsqualene sterol biosynthesis and related drugs

	K_i
	ERG2p S. cerevisiae [³H] Ifenprodil	ς₁ Receptor C. porcellus (+)-[³H] Pentazocine	EBP H. sapiens [³H] Ifenprodil
	nm
Sterol isomerase inhibitors
Fenpropimorph	0.05^4-a	0.011^4-b	44 ± 15
Tridemorph	0.09^4-a	0.039^4-b	1.3 ± 0.4
MDL28815	0.44^4-a	0.48^4-b	<0.54 ± 0.10^4-c
AY9944	5.8^4-a	0.50^4-b	12 ± 5
Triparanol	1.5^4-a	8.2^4-b	14 ± 4
Tamoxifen	1,470^4-b	34^4-b	2.8 ± 1.0
Zuclomiphene	1.6^4-b	4.7^4-b	3.0 ± 0.3
Enclomiphene	164^4-b	7.7^4-b	0.69 ± 0.11
Trifluperidol	0.15^4-b	0.83^4-b	354 ± 50
Sterol biosynthesis inhibitors
U18666A	0.10 ± 0.02	1.1 ± 0.3	1.9 ± 0.8
BM15766	16,480 ± 3,140	680 ± 90	34,000 ± 8,200
Naftifine	310 ± 25	880 ± 40	1,500 ± 40
Terbinafine	>50,000	N.D.	>50,000
Tamoxifen analogues
MDL5332	0.67 ± 0.24	3.2 ± 1.3	54 ± 27
Nafoxidine	232 ± 101	30 ± 14	0.9 ± 0.3

cDNAs encoding the guinea pig ς₁ receptor and the human EBP were expressed in yeast strain WA0 as described in Experimental Procedures. The affinities of the yeast ERG2p were determined as described (Moebius et al., 1996). Apparent slope factors close to 1 (0.80–1.20) were omitted for better clarity. Identical results as for the human EBP were obtained for the EBP from C. porcellus (not shown).

Data shown are mean ± standard deviation (n = 3). N.D., not determined.
↵4-a data taken from (Moebius et al., 1996)
↵4-b data taken from (Moebius et al., 1997a)
↵4-c apparent slope factor 2.27 ± 0.26.