2.2.2. Interdomain Hydrogen Bonding

Seven interdomain hydrogen bonds were observed in the crystal structure of monomers bound to NADPH(OH)<sup>2</sup> involving the residue pairs Asn2-Gly259 (Nt- α7/α8), Lys16- 238Tyr (β1/α1- α7), Asn145-Thr249 (β5/β6- α7/α8), Thr157-Lys359 (β6/β7- α12), Asp159- Lys359/His363 (β7- α12, α12/α13), Thr180-Arg241 (β8/α5- α7) and Pro184-Val188 (β8/α5- α5). During the simulations, five interdomain hydrogen bonds (with both NADP, NADPH bound) involve the residues of Nt [Leu1-Asn208/Asp209 (α5/α6) and Asn2-Gly259 (α7/α8)], β1 [Thr8-Asn253 (α7)], and β8/α5 [Thr180-Arg241 (α7), Pro184-Gln187/Val188 (α5)]. In addition, other hydrogen bonds involving residue pairs Thr142-Asp194 and Asp176-Tyr238 were observed in NADP-bound monomer. On average, three interdomain hydrogen bonds observed in the crystal structure between Asn2-Gly259, Thr180-Arg241 and Pro184- Val188 occurred frequently during the simulations. Observed changes in the hydrogen bonding interactions evidence conformational changes in the monomer to accommodate NADP/H cofactors.
