Citrate

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Crystal Structure Studies of Nadp+ Dependent Isocitrate Dehydrogenase from Thermus Thermophilus Exhibiting a Novel Terminal Domain

Journal Title, Volume, Page: 
Biochemical and Biophysical Research Communications Volume 449, Issue 1, Pages 107–113
Year of Publication: 
2014
Authors: 
Muneer Abdoh
epartment of Physics, Faculty of Science, An-Najah National University, Nablus, Palestine
Current Affiliation: 
Department of Physics, Faculty of Science, An-Najah National University, Nablus, Palestine
Kumar SM
Department of Studies in Physics, University of Mysore, Mysore 570 006, India
Pampa KJ
Department of Studies in Microbiology, University of Mysore, Mysore 570 006, India
Manjula M
Department of Studies in Physics, University of Mysore, Mysore 570 006, India
Kunishima N
Advanced Protein Crystallography Research Group, RIKEN SPring-8 Center, Harima Institute, Hyogo 679-5148, Japan
Lokanath NK
Department of Studies in Physics, University of Mysore, Mysore 570 006, India
Preferred Abstract (Original): 

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 ofThermus 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.

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