121st General Meeting of the KCS

Type Poster Presentation
Area Physical Chemistry
Room No. Event Hall
Time 4월 20일 (금요일) 11:00~12:30
Code PHYS.P-235
Subject Cooperative Protein Structural Dynamics of Homodimeric Hemoglobin Resolved by Time-Resolved X-ray Solution Scattering
Authors MINSEO CHOI, Hyotcherl Ihee*
Department of Chemistry, Korea Advanced Institute of Science and Technology, Korea
Abstract The hemoglobin is one of the most important protein in vertebrate, thus a lot of researches have studied while the allosteric structural transition and kinetic information. The homodimeric hemoglobin HbI is possible alternative model system of tetrameric HbI. We studied HbI protein to investigate directly the structural dynamics in the solution phase, using pump-probe X-ray solution scattering (TRXSS) to investigate the specific allosteric structural transition in real time and structural information such as rotation angle and heme-heme distance over time (100ps~10ms). We compared and analyzed the common points and differences among K30D, wild type and other mutants in terms of kinetic models by the tool of kinetic analysis. We built the kinetic models considering paths and time constants which were 4.01ns, 3.09ns, 439ns, 437us, 5.33ms. Since K30D is mutated aspartic acid to lysine for 30th amino acid so the salt bridge disappeared, the interaction force of dimeric interface was weaker than wild type. K30D went through dissociation and had equilibrium state existed both of dimer and monomer in solution before initiation by pump laser. It could be a reason of faster tertiary structural change of dimer’s intermediates I2-to-I3 transition than that of wild type though similarity of I1-to-I2 transition rate. According to our previous work [1], I1 and I2 had R-like structures and I3 had a T-like structure. So the results of K30D’s implicated that the transition from I2-to-I3 was accelerated which was suggested R-T transition, since it had feebler interface force. Lastly, bimolecular CO recombination with bimolecular rate constants was also faster than that of K30D’s, because of the same above reason.
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