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Figure 3
Segment of a sequence alignment of NTRs from different plants covering the two variable-loop segments in plant NTRs. The complete alignment can be found in Supplementary Fig. 11. The NTRs, with their accession numbers given in parentheses, are HvNTR1 (EU314717), HvNTR2 (EU250021) and HvNTRC from Hordeum vulgare (barley); TaNTR1 (Q8VX47) and TaNTR2 (TC297680) from Triticum aestivum (wheat); OsNTR1 (Q69PS6), OsNTR2 (Q6ZFU6) and OsNTRC (Q70G58) from Oryza sativa (rice); ZmNTR1 (EU966898), ZmNTR2 (BT054285) and ZmNTRC (BT037345) from Zea mays (maize); AtNTRA (Q39242), AtNTRB (Q39243) and AtNTRC (O22229) from Arabidopsis thaliana (mouse-ear cress); PtNTRA (AC149479), PtNTRB (XM_002317595) and PtNTRC (XM_002308899) from Populus trichocarpa (western balsam poplar); and MtNTRA and MtNTRC from Medicago truncatula (barrel medic, a legume). The sequences were aligned using ClustalW (Thompson et al., 1994BB41) and divided into four groups based on the phylogenetic analysis. Groups 1 and 2 are both monocotyledon subgroups of the A/B type, group 3 is the dicotyledon type A/B and group 4 is the subgroup of the C-type NTRs. Strictly conserved residues have a red background and residues that are well conserved within a group according to the Risler matrix (Risler et al., 1988BB33) are indicated by red letters. Residues conserved between groups are boxed. The secondary structure of HvNTR2 was added using ESPript (Gouet et al., 1999BB11) and coloured according to domain: the NADPH domain is in green and the β-sheet linker between the two domains is in pink. Residues assumed to make hydrogen bonds to NADPH are marked by stars and the active-site cysteines are marked by cyan circles. The B9–B10 and the B14–B15 loops show the largest structural variation in a superposition of the HvNTR2 and the AtNTR-B structures. The primary structure of AtNTR-B differs from the validated Q39243 sequence at positions 120 (I→T), 135 (V→A), 136 (L→S) and 329 (E→Q).

Journal logoBIOLOGICAL
ISSN: 1399-0047
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