TABLE 1.

Selectivity ratios of D-sites for MAPKs

D-site peptide	Cognate MAPK	Cognate IC50	Non-cognate MAPK	Non-cognate IC50	Selectivity ratioa
MEK1	ERK2	32	p38/MEF2Ab	>100	>3
MEK1	ERK2	32	p38/ATF2	90	3
MEK1	ERK2	32	JNK1	>100	>3
MEK1	ERK2	32	JNK2	>100	>3
				MEK1 mean	3
				MEK1 median	3
MEK2	ERK2	5	p38/MEF2A	40	8
MEK2	ERK2	5	p38/ATF2	NDc	ND
MEK2	ERK2	5	JNK1	60	12
MEK2	ERK2	5	JNK2	>100	>20
				MEK2 mean	13
				MEK2 median	12
MKK3	p38b	<0.1	JNK1	90	>900
MKK3	p38	<0.1	JNK2	>100	>1000
MKK3	p38	<0.1	ERK2	5	>50
				MKK3 mean	650
				MKK3 median	900
MKK4	JNK1	2	ERK2	26	13
MKK4	JNK2	9	ERK2	26	3
MKK4	p38/MEF2A	7	ERK2	26	4
MKK4	p38/ATF2	6	ERK2	26	4
				MKK4 mean	6
				MKK4 median	4
MKK6	p38/MEF2A	20	JNK1	>100	>5
MKK6	p38/MEF2A	20	JNK2	>100	>5
MKK6	p38/MEF2A	20	ERK2	17	1
MKK6	p38/ATF2	10	JNK1	>100	>10
MKK6	p38/ATF2	10	JNK2	>100	>10
MKK6	p38/ATF2	10	ERK2	17	2
				MKK6 mean	5
				MKK6 median	5
MKK7	JNK1	8	p38/MEF2A	>100	>13
MKK7	JNK1	8	ERK2	85	11
MKK7	JNK2	30	p38/MEF2A	>100	>3
MKK7	JNK2	30	ERK2	85	3
				MKK7 mean	7
				MKK7 median	7
				All mean	150
				All median	8

^aSelectivity ratio = IC₅₀ (D-site peptide with non-cognate MAPK)/IC₅₀ (D-site peptide with cognate MAPK).

^bThe p38 the substrate used is shown. For p38 inhibition by the MKK3 peptide, both substrates gave the same results.

^cND, not determined.