Nip7 protein structure. (A) 3D representation of the P. abyssi protein structure (2P38:A) . The secondary structure elements are lettered and colored (helices red, β-strands blue, turns green). The N-terminal domain left, C-terminal domain right. Amino acid residues assumed to bind an RNA molecule  shown as ball and stick representation. (B) Alignment of the P. abyssi and P. furiosus sequences. The substitutions in the P. furiosus relative to the P. abyssi protein are on gray background. Distinguished are the following types of substitutions resulting in replacement of: a polar residue in P. abyssi by a nonpolar in P. furiosus (red); a charged P. abyssi amino acid by an uncharged in P. furiosus at retained polarity (green); polar amino acid in P. furiosus by nonpolar in P. abyssi (pink); P. furiosus charged side group by an uncharged (lilac); those resulting in oppositely charged residues (blue). Secondary structure is shown below sequences according to 2P38:A: the helices are indicated in red rectangles, blue arrows indicate β-strands. Residues belonging to the interior of the protein according to the GetArea web-server  are shown in bold letters. The symbol *denotes amino acids involved in RNA binding . The N-terminal domain beneath the row of position numbers, blue; the C-terminal domain, red.