1. a
MELLFLGTGAGIPAKARNVTSVALKLLEERRSVWLFDCGEATQHQILHTT
IKPRKIEKIFITHMHGDHVYGLPGLLGSRSFQGGEDELTVYGPKGIKAFI
ETSLAVTKTHLTYPLAIQEIEEGIVFEDDQFIVTAVSVIHGVEAFGYRVQ
EKDVPGSLKADVLKEMNIPPGPVYQKIKKGETVTLEDGRIINGNDFLEPP
KKGRSVVFSGDTRVSDKLKELARDCDVLVHEATFAKEDRKLAYDYYHSTT
EQAAVTAKEARAKQLILTHISARYQGDASLELQKEAVDVFPNSVAAYDFL
EVNVPRG . . . . 50 b1 b2 b3 a1 . . . .
100 . b4 A a2 b5 a3 . . . .
150 a3 b6 b7 b8 b9 . .
absent in A . .
200 a4 a5
b10
b11 . . .
absent in B .
250
b12 a6
b13 a7 . . . .
300 a8
b14 a9
b15
307
b16 b
C-ter
N-ter
b16 b2 a1 a2 a3 b1 b3 b4 b5 b6 a4
b10 a5
b11 b7 b9 a6 a8 a9 b8
b12
b13
b14
b15 a7
Supplementary Figure 2. RNase Z secondary structure and topology. -strands are represented by green arrows, -helices by blue cylinders. (a) Secondary strucure superimposed on the protein sequence. Residues that could not be resolved in one or other subunit are shown in grey and their secondary structure features in red. Helix 2 is shorter in the A subunit and the start point is shown by the letter A. (b) Secondary structure topology showing opposing  motifs and insertions (in red) between 9 and 12 and 8 and 13.