Rpp20 has strong homology with ABC transporter ATPases (in particular a
putative ABC transporter ATPase from A. thaliana, see
below), and weak homology with a Upf1p subfamily of the DEAD-box
ATP-dependent RNA helicase superfamily. (A) Schematic
representation of the common motifs of Rpp20, the Upf1p subfamily, and
ABC transporters. The alignment of sequence conservation of ABC
transporter ATPase super family is described in ref. 12, and that of
the Upf1p family is reviewed in refs. 6 and 7. Fully conserved residues
are shown in uppercase, semiconserved in lowercase, and nonconserved
are designated as x. (B) Sequence alignment of Rpp20 and
the C-terminal fragment (starting at residue 163) of the ABC
transporter ATPase from A. thaliana. Identical residues
are marked by an asterisk; residues of high similarity by a colon; and
residues of low similarity by a period. Gaps are shown as dashed lines.