Structural domains comprising this superfamily share the structure of the all alpha-helical C-terminal domain of CarD from Mycobacterium tuberculosis (Mtb), an essential protein thought to be involved in stringent response through down-regulation of rRNA and ribosomal protein genes. CarD is DNA binding protein but the N-terminal domain is not involved in this process. Mutation studies have revealed that the C-terminal domain is the DNA interaction domain. The N-terminal domain of CarD is responsible for interaction with the beta-subunit of RNAP. This interaction is vital for Mtb's survival during the persistent infection state.