Unusually Strong H-Bonding to the Heme Ligand and Fast Geminate Recombination Dynamics of the Carbon Monoxide Complex of Bacillus subtilis Truncated Hemoglobin

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• 作者：Alessandro Feis ; Andrea Lapini ; Bruno Catacchio ; Silvia Brogioni ; Paolo Foggi ; Emilia Chiancone ; Alberto Boffi ; Giulietta Smulevich
• 刊名：Biochemistry
• 出版年：2008
• 出版时间：January 22, 2008
• 年：2008
• 卷：47
• 期：3
• 页码：902 - 910
• 全文大小：262K
• 年卷期：v.47,no.3(January 22, 2008)
• ISSN：1520-4995

文摘

The active site of the oxygen-avid truncated hemoglobin from Bacillus subtilis has beencharacterized by infrared absorption and resonance Raman spectroscopies, and the dynamics of COrebinding after photolysis has been investigated by picosecond transient absorption spectroscopy. ResonanceRaman experiments on the CO bound adduct revealed the presence of two Fe-CO stretching bands at545 and 520 cm^-1, respectively. Accordingly, two C-O stretching bands at 1924 and 1888 cm^-1 wereobserved in infrared absorption and resonance Raman measurements. The very low C-O stretchingfrequency at 1888 cm^-1 (corresponding to the extremely high RR stretching frequency at 545 cm^-1)indicates unusually strong hydrogen bonding between CO and distal residues. On the basis of a comparisonwith other truncated hemoglobin it is envisaged that the two CO conformers are determined by specificinteractions with the TrpG8 and TyrB10 residues. Mutation of TrpG8 to Leu deeply alters the hydrogen-bonding network giving rise mainly to a CO conformer characterized by a Fe-CO stretching band at 489cm^-1 and a CO stretching band at 1958 cm^-1. Picosecond laser photolysis experiments carried out on theCO bound adduct revealed dynamical processes that take place within a few nanoseconds after photolysis.Picosecond dynamics is largely dominated by CO geminate rebinding and is consistent with strongH-bonding contributions of TyrB10 and TrpG8 to ligand stabilization.