TABLE 2.

MICs determined by broth-dilution method for mtrE mutants expressed with mtrCD in E.coli (ΔtolC) TG1(DE3)

MtrE intra-protomer groove mutants (N198L, E434K and Q441E) are shown in bold; underline indicates faint growth; antibiotic abbreviations are Pen, penicillin G; Naf, nafcillin; Tet, tetracycline; Ery, erythromycin; Nov, novobiocin; and Van, vancomycin; and for studies of the simultaneous effects of nafcillin and vancomycin, the MIC for vancomycin was determined in the presence of 1 μg/ml nafcillin.

Constructs	Pen	Naf	Tet	Ery	Nov	Van	Van (+ 1 μg/ml Naf)
	μg/ml	μg/ml	μg/ml	μg/ml	μg/ml	μg/ml	μg/ml
Vector pACYC	16	1.5625	<0.5	2	<0.5	512	128
MtrE WT-CD	64	32	12.5	64	2	512	8
MtrE N198L-CD	32	8	<0.5	2	1	256	8
MtrE Q441E-CD	16	1	<0.5	64	<0.5	64	8
MtrE E434K-CD	16	1	<0.5	64	<0.5	64	8
MtrE R239K-CD	64	32	12.5	<0.5	2	256	8
MtrE K397E-CD	64	32	12.5	<0.5	2	256	8