[Role of histidine in ligand binding ability of hemoglobin gene].
The atomic and electronic structures of heme complexes with His, Gly, and Cys residues (Heme-His, Heme-Gly, and Heme-Cys) in the fifth coordination position of the Fe atom and with oxygen and nitrogen oxide molecules in the sixth Fe position were studied by the semiempirical quantum-chemical method PM3. A comparative analysis of internuclear distances showed that the strength of chemical bonding between the ligand molecules (oxygen and nitrogen oxide) is greater for Heme-Cys than for Heme-His and Heme-Gly complexes. Consequently, the strengthening of the chemical bond of the oxygen (or nitrogen oxide) molecule with Heme-Cys substantially weakens the chemical bond in the ligand molecule. The Mulliken population analysis showed that the electronic density of ligand (oxygen or nitrogen oxide) p-orbitals is transferred to the d-orbitals of the Fe atom, whose charge, calculated according to the Mulliken analysis, formally becomes negative. In the Heme-His complex with oxygen, this charge is substantially greater than in the complex with NO, and the oxygen molecule becomes polarized. No oxygen polarization is observed in the Heme-Cys complex, and the electron density (judging from the change in the Fe charge) is transferred to the coordinated sulfur atom. This is also characteristic of Heme-Cys complexes with nitrogen oxide. An analysis of charges on the atoms indicates that the character of chemical bonding of the oxygen molecule in Heme-Cys and Heme-Gly complexes is similar and basically differs from that in the case of the Heme-His complex. The English version of the paper: Russian Journal of Bioorganic Chemistry, 2004, vol. 30, no. 2; see also http://www.maik.ru.
Romanova
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TA
Institute of Computational Modeling, Kirenskii Institute of Physics, Siberian Division, Russian Academy of Sciences, Akademgorodok, Krasnoyarsk, 660036 Russia. romanova@iph.krasn.ru
Krasnov
P O
PO
Kuzubov
A A
AA
Avramov
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PV
D006454:Hemoglobins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D006639:Histidine / Q000378:metabolism / Q000502:physiology*; D008024:Ligands; D008958:Models, Molecular; D011485:Protein Binding
D006454:Hemoglobins; D008024:Ligands; D006639:Histidine