A subunit of human nuclear RNase P has ATPase activity

Human nuclear RNase P purified from HeLa cells has ATPase activity. This ac tivity is associated with one of the protein subunits of the enzyme, Rpp20. Thus, human nuclear RNase P, which contains several proteins and one essen tial RNA, has at least one other enzymatic activity in addition to cleavage of phosphoester bonds in RNA. The amino acid sequence of Rpp20 has a signa ture motif found in an ATPase-containing subunit of a family of protein com plexes (ABC transporters) that mediate a variety of transmembrane traffic, as well as a segment, DlxxN, that resembles the DEAD box motif of many ATPa ses: together, these might represent an ATPase signature motif.