Complex sentence: In archaeabacteria, the Rrp41 subunit of the complex, a phosphorolytic exoribonuclease which is present three times in the ring, is responsible for the activity of the complex.
Split into simpler sentences: In archaeabacteria, the Rrp41 subunit of the complex is a phosphorolytic exoribonuclease. Three copies of this protein are present in the ring and this enzyme is responsible for the activity of the complex.