Concerted mechanism upon substitution of hydrogen sulfide by oxygen or cyanide binding to an unusual hemoglobin from lucina pectinata

摘要

Hemoglobin I (HbI) from the clam Lucina pectinata has the unusual ability to bind hydrogen sulfide. This heme protein that carries out its function, by transporting H_2S to a bacteria symbion, in a hydrogen-sulfide bound ferric state [1]. The HbI protein has a high content of phenyl residues in the heme pocket that may account for its ligand binding properties. To explore this, resonance Raman spectroscopy was used to determine the heme structure of deoxy, oxy, carbon monoxy, metaquo, and methydrogen sulfide HbI complexes. The oxidation (4), spin (3) and coordination (2) markers were identified in the high frequency spectra of all the HbI derivatives. The data indicated that the aromatic environment near the heme does not affect the iron oxidation state, coordination state, spin state, and core size marker vibrational modes. The marker bands also revealed that metsulfide HbI complex has a Fe(III), six coordinate, and low spin structure. The low frequency vibrational frequencies for the HbISH_2, HbIO_2 and HbICO derivatives showed Fe-S at 374 cm~(-1), Fe-O at 563 cm~(-1), and Fe-C 516 cm~(-1), respectively [2,3].