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# GroEL is involved in activation of Escherichia coli RNA polymerase devoid of the \omega subunit in vivo

Mukherjee, Kakoli and Nagai, Hiroki and Shimamoto, Nobuo and Chatterji, Dipankar (1999) GroEL is involved in activation of Escherichia coli RNA polymerase devoid of the \omega subunit in vivo. In: European Journal of Biochemistry, 266 (1). pp. 228-235.

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Highly purified Escherichia coli RNA polymerase contains a small subunit termed \omega that has a molecular mass of 10 105 Da and is comprised of 91 amino acids. E. coli strains lacking \omega (\omega-less) are viable, but exhibit a slow-growth phenotype. Renaturation of RNA polymerase isolated from an \omega-less mutant, in the presence of \omega, resulted in maximum recovery of activity. The \omega-less RNA polymerase from \omega-less strains recruits the chaperonin, GroEL (unlike the wild-type enzyme), suggesting a structural deformity of the mutant enzyme. The GroEL-containing core RNA polymerase interacts efficiently with $\sigma^7^0$ to generate the fully functional holoenzyme. However, when GroEL was removed, the enzyme was irreversibly nonfunctional and was unable to bind to $\sigma^7^0$. The damaged enzyme regained activity after going through a cycle of denaturation and reconstitution in the presence of \omega or GroEL. GroES was found to have an inhibitory effect on the core-$\sigma^7^0$ association unlike the \omega subunit. The \omega subunit may therefore be needed for stabilization of the structure of RNA polymerase.