Crystal structure studies of NADP+ dependent isocitrate dehydrogenase from Thermus thermophilus exhibiting a novel terminal domain.

NADP(+) dependent isocitrate dehydrogenase (IDH) is an enzyme catalyzing oxidative decarboxylation of isocitrate into oxalosuccinate (intermediate) and finally the product α-ketoglutarate. The crystal structure of Thermus thermophilus isocitrate dehydrogenase (TtIDH) ternary complex with citrate and cofactor NADP(+) was determined using X-ray diffraction method to a resolution of 1.80 Å. The overall fold of this protein was resolved into large domain, small domain and a clasp domain. The monomeric structure reveals a novel terminal domain involved in dimerization, very unique and novel domain when compared to other IDH's. And, small domain and clasp domain showing significant differences when compared to other IDH's of the same sub-family. The structure of TtIDH reveals the absence of helix at the clasp domain, which is mainly involved in oligomerization in other IDH's. Also, helices/beta sheets are absent in the small domain, when compared to other IDH's of the same sub family. The overall TtIDH structure exhibits closed conformation with catalytic triad residues, Tyr144-Asp248-Lys191 are conserved. Oligomerization of the protein is quantized using interface area and subunit-subunit interactions between protomers. Overall, the TtIDH structure with novel terminal domain may be categorized as a first structure of subfamily of type IV.

5-(Prop-2-yn-1-yl)-5H-dibenzo[b,f]azepine: ortho-rhom-bic polymorph.

In the title ortho-rhom-bic polymorph (space group Iba2), C17H13N, the dihedral angle between the benzene rings is 55.99 (10)° and the azepine ring adopts a boat conformation. In the crystal, mol-ecules are linked by C-H⋯π contacts. The previously-reported polymorph [Yousuf et al. (2012 ▶). Acta Cryst. E68, o1101] crystallizes in the monoclinic system (space group P21/c) with two mol-ecules in the asymmetric unit.

[4-(4-Meth-oxy-phen-yl)-2-(pyridin-3-yl)-1,3-thia-zol-5-yl][4-(tri-fluoro-meth-yl)phen-yl]methanone.

In the title compound, C23H15F3N2O2S, the thia-zole ring makes dihedral angles of 12.98 (13), 49.30 (11) and 49.83 (12)° with the pyridine ring, the meth-oxy-phenyl ring and the (tri-fluoro-meth-yl)phenyl ring, respectively. In the crystal, mol-ecules are connected via C-H⋯O hydrogen bonds, forming chains along [010]. There are also C-H⋯π and C-F⋯π inter-actions present, forming a three-dimensional structure.

(E)-N'-[1-(Thio-phen-2-yl)ethyl-idene]isonicotinohydrazide.

In the title compound, C(12)H(11)N(3)OS, the dihedral angle between the pyridine and thio-phene rings is 46.70 (9)° and the C-N-N-C torsion angle is 178.61 (15)°. In the crystal, inversion dimers linked by pairs of N-H⋯O hydrogen bonds generate R(2) (2)(8) loops.

Ethyl 1-aminona-phtho[2,1-b]furan-2-carboxyl-ate.

In the title compound, C(15)H(13)NO(3), there is intra-molecular N-H⋯O hydrogen bond between the amino group and the ester carbonyl O atom and the dihedral angle between the aromatic ring and the ester group is 2.05 (15)°. In the crystal, mol-ecules are connected by N-H⋯O hydrogen bonds into chains parallel to [010]. In addition there are short C-H⋯O inter-actions and π-π stacking inter-actions with a distance of 3.555 (2) Šbetween the centroids of the furan and benzene rings.

Ethyl 2-cyano-5-oxo-5-(thio-phen-2-yl)-3-(3,4,5-trimeth-oxy-phen-yl)penta-noate.

In the title compound, C21H23NO6S, the dihedral angle between the thio-pene and benzene rings is 88.66 (6)°. In the crystal, mol-ecules are connected by C-H⋯N and C-H⋯O hydrogen bonds, forming a tape along [10-1]. In addition, C-H⋯π and π-π stacking [centroid-centroid distance = 3.879 (2) Šbetween the thio-phene rings] inter-actions are observed.

2,6-Dichloro-phen-yl 4-chloro-benzoate.

In the title compound, C13H7Cl3O2, the dihedral angle between the benzene rings is 82.1 (2)°. The dihedral angle between the CO2 group and its carbon-bonded ring is 14.50 (19)° In the crystal, aromatic π-π stacking inter-actions [minimum ring centroid separation = 3.604 (2) Å] occur.

1H-Indole-3-carbaldehyde.

In the title compound, C(9)H(7)NO, the benzene ring forms a dihedral angle of 3.98 (12)° with the pyrrole ring. In the crystal, N-H⋯O hydrogen bonds links the mol-ecules into chains which run parallel to [02-1].

4-[(3-Chloro-2-methyl-phen-yl)imino-meth-yl]phenol.

In the title compound, C(14)H(12)ClNO, the dihedral angle between the aromatic rings is 39.84 (7)°. In th crystal, mol-ecules are connected by O-H⋯N hydrogen bonds into chains parallel to [001]. In addition, a C-H⋯π contact occurs.