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Ligand Migration and Binding in Non-Symbiotic Hemoglobins of Arabidopsis thaliana

Nienhaus, K.; Dominici, P.; Astegno, A.; Abbruzzetti, S.; Viappiani, C.; Nienhaus, G. U.

We have studied carbon monoxide (CO) migration and binding in the nonsymbiotic hemoglobins AHb1 and AHb2 of Arabidopsis thaliana using Fourier transform infrared (FTIR) spectroscopy combined with temperature derivative spectroscopy (TDS) at cryogenic temperatures. Both proteins have similar amino acid sequences but display pronounced differences in ligand binding properties, at both physiological and cryogenic temperatures. Near neutral pH, the distal HisE7 side chain is close to the heme-bound ligand in the majority of AHb1-CO molecules, as indicated by a low CO stretching frequency at 1921 cm-1. In this fraction, two CO docking sites can be populated, the primary site B and the secondary site C. When the pH is lowered, a high-frequency stretching band at 1964 cm-1 grows at the expense of the low-frequency band, indicating that HisE7 protonates and, concomitantly, moves away from the bound ligand. Geminate rebinding barriers are markedly different for the two conformations, and docking site C is not accessible in the low-pH conformation. Rebinding of NO ligands was observed only from site B of AHb1, regardless of conformation. In A ... mehr

DOI: 10.1021/bi100768g
Zitationen: 17
Web of Science
Zitationen: 17
Zugehörige Institution(en) am KIT Institut für Angewandte Physik (APH)
Publikationstyp Zeitschriftenaufsatz
Jahr 2010
Sprache Englisch
Identifikator ISSN: 0006-2960
KITopen-ID: 1000027201
Erschienen in Biochemistry
Band 49
Heft 35
Seiten 7448-7458
Nachgewiesen in Web of Science
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