KAIST

Professor Hak-Sung Kim

-“Solved the 50 year old mystery of how protein recognises and binds to ligands”

- Exciting potential for understanding life phenomena and the further development of highly effective therapeutic agent development

KAIST’s Biological Science Department’s Professor Hak-Sung Kim, working in collaboration with Professor Sung-Chul Hong of Department of Physics, Seoul National University, has identified the mechanism of how the protein recognizes and binds to ligands within the human body.

The research findings were published in the online edition of Nature Chemical Biology (March 18), which is the most prestigious journal in the field of life science.

Since the research identified the mechanism, of which protein recognises and binds to ligands, it will take an essential role in understanding complex life phenomenon by understanding regulatory function of protein. 

Also, ligand recognition of proteins is closely related to the cause of various diseases. Therefore the research team hopes to contribute to the development of highly effective treatments.

Ligands, well-known examples include nucleic acid and proteins, form the structure of an organism or are essential constituents with special functions such as information signalling.

In particular, the most important role of protein is recognising and binding to a particular ligand and hence regulating and maintaining life phenomena. The abnormal occurrence of an error in recognition of ligands may lead to various diseases.

The research team focused on the repetition of change in protein structure from the most stable “open form” to a relatively unstable “partially closed form”.  

Professor Kim’s team analysed the change in protein structure when binding to a ligand on a molecular level in real time to explain the ligand recognition mechanism.

The research findings showed that ligands prefer the most stable protein structure. The team was the first in the world to identify that ligands alter protein structure to the most stable, the lowest energy level, when it binds to the protein.

In addition, the team found that ligands bind to unstable partially-closed forms to change protein structure.

The existing models to explain ligand recognition mechanism of protein are “Induced Custom Model”, which involves change in protein structure in binding to ligands, and the “Structure Selection Model”, which argues that ligands select and recognise only the best protein structure out of many. The academic world considers that the team’s research findings have perfectly proved the models through experiments for the first time in the world.

Professor Kim explained, “In the presence of ligands, there exists a phenomenon where the speed of altering protein structure is changed. This phenomenon is analysed on a molecular level to prove ligand recognition mechanism of protein for the first time”. He also said, “The 50-year old mystery, that existed only as a hypothesis on biology textbooks and was thought never to be solved, has been confirmed through experiments for the first time.”

Figure 1: Proteins, with open and partially open form, recognising and binding to ligands.

Figure 2: Ligands temporarily bind to a stable protein structure, open form, which changes into the most stable structure, closed form. In addition, binding to partially closed form also changes protein structure to closed form.