), the two most stable variants, I54A 32 and L47Q/ L55Q 32, whose half-lives are 9-fold and more than 10-fold longer than that of the wild type, respectively, were examined in an in vitro degradation system using ClpYQ and FtsH proteases. As expected from high 32 activity in vivo (26), the purified 32 mutants were co-fractionated with core RNA polymerase like wild-type 32 using gel filtration (sup