Sequence alignment of the NBD1 and NBD2 of human CFTR, obtained by slightly adjusting the sequence alignment presented by Lewis and coworkers[9]based on the
crystal structure of human CFTR’s NBD1. The alignment shows a sequence identity of 24.8% and a similarity of 43.6% between NBD1 and NBD2. The ‘‘*’’ symbols represent
identical amino acid residues, and the ‘‘þ’’ symbols show residue pairs with positive BLOSUM62 matrix scores, representing similar sequence alignment. The prominent
consensus sequences among the ABC transporter superfamily are highlighted. Among them, Walker A and Walker B are highly conserved nucleotide binding motifs in many
proteins. The Signature sequence is a unique sequence that characterizes the ABC transporters. See Ref.[4]for detailed explanations