Table 1. Sensitivity of β 531 mutant RNAP to Rif (25 μg/ml) in vitro.

RNAP	Residual activity (%)	Rif resistance*
531S (WT)	1.4	−
531A	0.8	−
531C	4.0	+
531D	76.2	+++
531E	69.0	+++
531F	66.7	+++
531G	2.7	±
531I	7.2	+
531K	35.0	++
531L	45.2	+++
531M	57.0	+++
531N	20.0	++
531P	9.3	++
531Q	60.0	+++
531R	15.2	++
531T	1.2	−
531V	4.2	+
531W	51.0	+++
531Y	80.0	+++

* ‘−’, <2%; ‘±’, 2–3%; ‘+’, 3–8%; ‘++’, 8–35%; ‘+++’, >35% activity.