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Seminar/Colloquim

PHYSICS/BK21 Colloquium[09.10.16]

본문



Toward an Unified Description for Thermodynamics,
    Folding Kinetics, and Mutagenesis of Proteins”

* Speaker : Prof. Ik Soo Chang[Pusan National University]
* Place : Physics Seminar Room (Science Bldg, 3-201)
* Date & Time : Oct,  16Fri)  4:00 ~ 5:00 pm
 
Abstract
A multiscale-heterogeneous protein energy function was developed for the biophysical study of the
thermodynamics, folding kinetics, and mutagenesis of proteins. After hybridizing an  atomic  force-
field into a coarse-grained energy function to account for the specificity of a  sequence  of  amino
acids even with the high structural homology, we constructed an exact free energy landscape of a
given protein and characterized its thermodynamics and folding-unfolding kinetics via  a  Chevron
plot based on solving exactly a master equation, which would enable us to pursue  a  mutagenesis
application. Our approach was applied successfully for resolving a controversy  about  the  folding
mechanism of fast folding proteins.  

Recent experiments claiming that BBL protein follows a global downhill folding raised an important
controversy as to the folding mechanism of fast folding proteins. Under the global downhill folding
scenario not only proteins undergo a gradual folding, but also folding events along the continuous
folding pathway could be mapped out from the equilibrium denaturation experiment. Based on the
exact calculation using a free energy landscape, relaxation eigenmodes from  a  master  equation,
and Monte Carlo simulation of an  extended  Munoz-Eaton  model  that  incorporates  multiscale-
heterogeneous pairwise-interactions between amino acids, here we show that the very nature of a
two-state cooperative transition such as a bimodal distribution from an exact free energy landscape
and biphasic relaxation kinetics do manifest in the thermodynamics  and  folding-unfolding  kinetics
of BBL and peripheral subunit-binding domain (PSBD) homologue. Our results provide an unequivocal
resolution to the fundamental controversy related to  the  global  downhill  folding  scheme,  whose
applicability to other proteins should be critically re-examined.

Contact Person : Prof. Ki Bong Lee (054-279-2068, kibong@postech.ac.kr)

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