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Crystal structure of ferric complex of the yellow lupin leghemoglobin with isoquinoline at 1.8 Å resolution
T. N. Safonova, A. V. Teplyakov, G. V. Obmolova, A. N. Popov, I. P. Kuranova, E. G. Harutyunyan
A. V. Shubnikov Institute of Crystallography, Academy of Sciences of the USSR, Moscow
Abstract: Complex of leghemoglobin with isoquinoline (Lb-IQ) is of interest with respect to the bulky ligand location in the heme pocket. The atomic model was refined (1.8 Å resolution) by a restrained parameter least-square procedure to a R factor of 0.18. The angle between the heme and ligand planes is 104°, the non-coplanarity apparently being due to the heme pocket size. The atom nearest to Fe is one of C atoms (Fe–C distance is 1.7 Å) but not the N atom of the ligand as was supposed previously. The imidazole ring of the proximal His F11 residue is not positionally affected as compared with deoxy-Lb. In both complexes the Fe atom is displaced from the heme plane towards the proximal His residue, distance between Fe and the heme plane being 0.08 Å. The-isoquinoline binding causes conformational changes, leading to some alterations in hydrogen bonds. The model includes 166 water molecules.
Russian Journal of Bioorganic Chemistry 1991, 17 (12):1605-1612