The stoichiometry of these subunits in the ACC holoenzyme differs amongst organisms. Other auxiliary factors are known to be part of the holoenzyme. An enzyme together with the cofactor(s) required for activity is called a "holoenzyme" (or haloenzyme). Prokaryotic polymerases exist in two forms&colon; core polymerase and holoenzyme. RNA polymerase is composed of a core and a holoenzyme structure. The above promoter sequences are recognized only by RNA polymerase holoenzyme containing sigma-70. Two years later, the first cryo-electron microscopy (cryo-EM) structure of telomerase holoenzyme ("Tetrahymena") was determined. The processed caspase-9 stays bound to the apoptosome complex, forming a holoenzyme. The sigma factor, together with RNA polymerase, is known as the RNA polymerase holoenzyme. DNA polymerase III holoenzyme is the primary enzyme complex involved in prokaryotic DNA replication. The RNA polymerase core associates with the sigma factor to form RNA polymerase holoenzyme. The holoenzyme is composed of a specific component known as the sigma factor. The classical PKA holoenzyme structure consists of two regulatory subunits and two catalytic subunits.