Research Results

• Date & Time: Friday, January 20, 2023, 5pm-6pm
• Place: Sugimoto Campus, Science Building, Room E211 (Lecture Room 10)
• Speaker: Dr. Nami Yamano (Renmin University of China)
• Title of the Lecture
  「脂質ナノディスクを利用した光合成アンテナ蛋白質の構造機能研究」

 Mr./Ms. Yamano, who received a degree from the Department of Chemistry at Renmin University of China and is currently a postdoctoral researcher at Renmin University of China, will give a lecture on her recent research results on the occasion of her short-term visit to Japan. We look forward to your participation.

Caretaker: Ritsuko Fujii (ext. 3624) E-mail: ritsuko[at]omu.ac.jp (Change [at] to @)

Abstract

 Photosynthesis is a reaction that uses the light (excitation) energy of sunlight to produce sugars from water and carbon dioxide. This uptake of sunlight is achieved by antenna proteins that bind chlorophyll and carotenoids as complementary molecules in the thylakoid membrane lipids. Interestingly, antenna proteins are involved not only in focusing light, but also in deactivating excess excitation energy in the membrane in response to changes in the intensity of fluctuating sunlight. Although it is known that this quenching process is caused by changes in the excited state of dye molecules induced by interprotein aggregation or changes in peripheral physical properties, there is a difference between molecular function analysis using isolated proteins as Mr./Ms. and macroscopic analysis results of leaves and thylakoid membranes, and the molecular mechanism of accurate focusing and quenching of antenna proteins in thylakoid membranes is unknown.
 In general, functional analysis of photosynthetic proteins is performed by dispersing isolated proteins in water as surfactant micelles, but the permeability of polar molecules and ions is high and it is difficult to say that the biological environment is reproduced. Liposomes have been widely used as systems that mimic hydrophobic membrane environments, but it is difficult to control random interprotein aggregation, and there is a problem that individual molecules form a heterogeneous excited state. Therefore, in this study, we attempted to reconstruct the antenna protein into a lipid bilayer layer called a lipid membrane nanodisk. Nanodisks can control the number of discs and contained proteins by adjusting the length of the cross-linked proteins, and it is possible to analyze the function of a single molecule while reproducing the lipid environment. Using nanosecond time-resolved absorption and fluorescence lifetime measurements, we investigated how the energy transfer and structure between dyes bound to antenna proteins differed compared to those in general surfactant micelles. As a result, it was clarified that the lipid membrane was in a conformation state that was more biased toward the quenching state than that of the micelle system.

（Bibliography: Yamano et al., J. Phys. Chem. B, 126(14):2669-2676, 2022.）

 It was held face-to-face with infection prevention measures. About 30 people participated and discussed. Thank you very much.