Scientific Results

Role of Local Structure and Dynamics of Small Ligand Migration in Proteins: A Study of a Mutated Truncated Hemoprotein from Thermobifida fusca by Time Resolved MIR Spectroscopy

Year: 2014

Authors: Patrizi B., Lapini A., Di Donato M., Marcelli A., Lima M., Righini R., Foggi P., Baiocco P., Bonamore A., Boffi A.

Autors Affiliation: LENS (European Laboratory for Nonlinear Spectroscopy) Via N. Carrara 1, Sesto Fiorentino, Florence 50019, Italy; Dipartimento di Chimica, Università di Firenze, via della Lastruccia 3-13, Sesto Fiorentino, Florence 50019, Italy; INO (Istituto Nazionale di Ottica), Largo Fermi 6, Firenze, Florence 50125, Italy; Dipartimento di Chimica, Università di Perugia, via Elce di Sotto 8, Perugia, Umbria 06123 Italy; Istituto Pasteur, Fondazione Cenci Bolognetti c/o Dipartimento di Scienze Biochimiche, Università “La Sapienza”, piazzale Aldo Moro 5, Rome, Rome 00185, Italy; Istituto Italiano di Tecnologia, Center of Nano Life Sciences, Viale Regina Elena 291, Rome, Rome 00161 Italy

Abstract: Carbon monoxide recombination dynamics in a mutant of the truncated hemoglobin from Thermobida fusca (3F-Tf-trHb) has been analyzed by means of ultrafast Visible-pump/MidIR-probe spectroscopy and compared with that of the wildtype protein. In 3F-Tf-trHb, three topologically relevant amino acids, responsible for the ligand stabilization through the formation of a H-bond network (TyrB10 TyrCD1 and TrpG8), have been replaced by Phe residues. X-ray diffraction data show that Phe residues in positions B10 and G8 maintain the same rotameric arrangements as Tyr and Trp in the wild-type protein, while Phe in position CD1 displays significant rotameric heterogeneity. Photodissociation of the ligand has been induced by exciting the sample with 550 run pump pulses and the CO rebinding has been monitored in two mid-IR regions respectively corresponding to the nu(CO) stretching vibration of the iron-bound CO (1880-1980 cm(-1)) and of the dissociated free CO (2050-2200 cm(-1)). In both the mutant and wild-type protein, a significant amount of geminate CO rebinding is observed on a subnanosecond time scale. Despite the absence of the distal pocket hydrogen-bonding network, the kinetics of geminate rebinding in 3F-Tf-trHb is very similar to the wild-type, showing how the reactivity of dissociated CO toward the heme is primarily regulated by the effective volume and flexibility of the distal pocket and by caging effects exerted on the free CO on the analyzed time scale.

Journal/Review: JOURNAL OF PHYSICAL CHEMISTRY B

Volume: 118 (31)      Pages from: 9209  to: 9217

More Information: We acknowledge the Helmholtz-Zentrum Berlin-Electron storage ring BESSY II for provision of synchrotron radiation at beamline BL 14-1, the italian MIUR (grants FIRB-Futuro in Ricerca 2010 RBFR109ZHQ and RBFR10Y5VW), Regione Toscana through PORFSE 2007-2013 project EPHODS) and Project EFOR-CABIR.
DOI: 10.1021/jp504499b

Citations: 1
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English