Heme methyl 1H chemical shifts as structural parameters in some low-spin ferriheme proteins |
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| Authors: | I Bertini Claudio Luchinat Giacomo Parigi F Ann Walker |
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| Institution: | (1) Center for Magnetic Resonance, Department of Chemistry University of Florence, via Sacconi 6, I-50019 Sesto Fiorentino (Fl), Italy e-mail: bertini@cerm.unifi.it Tel.: +39-055-4209272 Fax: +39-055-4209271, IT;(2) Department of Soil Science and Plant Nutrition, University of Florence, P. le delle Cascine, Florence, Italy, IT;(3) Department of Chemistry, University of Arizona, Tucson, AZ 85721, USA, US |
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| Abstract: | The different paramagnetic shifts of the four methyl groups in ferriheme proteins have been described as being due to the
effect of the axial ligand nodal plane orientation. An equation, heuristically found and theoretically explained, describing
the relation between contact and pseudocontact shifts and the position of the axial ligand(s) has been derived for bis-histidine
ferriheme proteins and for cyanide-histidine ferriheme proteins. The values of the heuristic parameters contained in the equations
were found by fitting the shifts of bovine cytochrome b
5 and several bis-histidine cytochromes c
3 and histidine-cyanide systems. The agreement between the observed and the calculated shifts was found to be good. Therefore,
by taking advantage of this study, information on the position of the axial ligands, that can be used as a constraint for
structure determination, can be obtained from the shifts of the methyl protons.
Received: 13 April 1999 / Accepted: 4 June 1999 |
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| Keywords: | Heme protein Nuclear magnetic resonance Paramagnetic shifts Axial ligand |
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