Structure of the Fe-heme in the homodimeric Hb from Scapharca Inequivalvis and in the T72I mutant: a XAS study at low temperature
| Autor: | S. Della Longa, A. Gambacurta §, A. Bertollini $, M. Girasole, A. Congiu-Castellano, F. Ascoli $ |
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| Jazyk: | angličtina |
| Rok vydání: | 2001 |
| Zdroj: | European biophysics journal 29 (2001): 559–568. doi:10.1007/s002490000102 info:cnr-pdr/source/autori:S. Della Longa *, A. Gambacurta §, A. Bertollini $, M. Girasole #, A. Congiu-Castellano ^, and F. Ascoli $/titolo:Structure of the Fe-heme in the homodimeric Hb from Scapharca Inequivalvis and in the T72I mutant: a XAS study at low temperature/doi:10.1007%2Fs002490000102/rivista:European biophysics journal/anno:2001/pagina_da:559/pagina_a:568/intervallo_pagine:559–568/volume:29 |
| DOI: | 10.1007/s002490000102 |
| Popis: | The Fe site structure in the recombinant wild-type and T72I mutant of the cooperative homodimeric hemoglobin (HbI) of the mollusc Scapharca inaequivalvis, has been investigated by measuring the Fe K-edge X-ray Absorption Near Edge Structure (XANES) spectra of their oxy, deoxy and carbomonoxy derivatives, and the cryogenic photoproducts of the carbomonoxy derivatives at T=12K. According to our results, the Fe site geometry in T72I HbI-CO is quite similar to that of human carbomonoxy hemoglobin (HbA-CO), while in native HbI-CO it seems intermediate between that of HbA-CO and sperm whale MbCO. The XANES spectra of oxy and deoxy derivatives are similar to the homologous spectra of human HbA, except for T72I HbI, for which the absorption edge is blue-shifted (about +1 eV) towards the spectrum of the oxy form. XANES spectra of the cryogenic photoproducts of HbA-CO (HbA*), HbI-CO (HbI*)and mutant HbI-CO (T72I HbI*) were acquired under continuous illumination at 12K. The Fe-heme structures of the three photoproducts are similar; however, while in the case of HbA* and HbI* the data indicate incomplete structural relaxation of the Fe-heme towards its deoxy-like (T) form, the relaxation in T72I HbI* is almost complete towards the proposed "high affinity" Fe-heme structure of T72I HbI. This evidence suggests that minor tertiary restraint affects the Fe-heme dynamics of T72I HbI, so that the observed dramatic enhancement in oxygen affinity of this hemoprotein, and the decreasing of cooperativity, could be explained, at the Fe site level, by a reduction of the proximal work necessary for the T->R transition. |
| Databáze: | OpenAIRE |
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