Following ligand migration pathways from picoseconds to milliseconds in type II truncated hemoglobin from Thermobifida fusca.
CO recombination kinetics has been investigated in the type II truncated hemoglobin from Thermobifida fusca (Tf-trHb) over more than 10 time decades (from 1 ps to ∼100 ms) by combining femtosecond transient absorption, nanosecond laser flash photolysis and optoacoustic spectroscopy. Photolysis is followed by a rapid geminate recombination with a time constant of ∼2 ns representing almost 60% of the overall reaction. An additional, small amplitude geminate recombination was identified at ∼100 ns. Finally, CO pressure dependent measurements brought out the presence of two transient species in the second order rebinding phase, with time constants ranging from ∼3 to ∼100 ms. The available experimental evidence suggests that the two transients are due to the presence of two conformations which do not interconvert within the time frame of the experiment. Computational studies revealed that the plasticity of protein structure is able to define a branched pathway connecting the ligand binding site and the solvent. This allowed to build a kinetic model capable of describing the complete time course of the CO rebinding kinetics to Tf-trHb.
LENS, European Laboratory for Non-linear Spectroscopy, Florence, Italy. marcelli@lens.unifi.it
Agnese
A
Marcelli
Stefania
S
Abbruzzetti
Juan Pablo
JP
Bustamante
Alessandro
A
Feis
Alessandra
A
Bonamore
Alberto
A
Boffi
Cristina
C
Gellini
Pier Remigio
PR
Salvi
Dario A
DA
Estrin
Stefano
S
Bruno
Cristiano
C
Viappiani
Paolo
P
Foggi
D000192:Actinomycetales / Q000378:metabolism*; D002248:Carbon Monoxide / Q000378:metabolism; D007700:Kinetics; D008024:Ligands; D010782:Photolysis; D011485:Protein Binding; D013997:Time Factors; D054793:Truncated Hemoglobins / Q000378:metabolism*
D008024:Ligands; D054793:Truncated Hemoglobins; D002248:Carbon Monoxide