Hydrophobic mismatch between α-crystallins and lipid bilayers

Jui-Kai Chen¹, Jheng-Hao Lin¹, Yu-Ting Liu², Ching-Hsun Yang¹, Ming-Tao Lee^1,2*

¹Scientific Research Division, National Synchrotron Radiation Research Center, Hsinchu, Taiwan
²Department of Physics, National Central University, Taoyuan, Taiwan

* Presenter:Ming-Tao Lee, email:mtlee@nsrrc.org.tw

αA-crystallin and αB-crystallin, the water soluble proteins, are able to carry out their chaperone function to maintain the transparency of eye lens. The cataract, induced by light scattering from eye lens clouding, is the major cause of the blindness. Previous studies show denature of α-crystallins cause abnormal aggregation of proteins and consequently lead to eye lens clouding. The mechanism is still a puzzle. Besides protein structure, the interaction between α-crystallins and membranes have been considered as possible mechanism of the function loss. In this study, the different thicknesses of lipid bilayers composed of Di18:1PC (DOPC) and Di20:1PC are used to interact with α-crystallins. The lamellar X-ray diffraction (LXD) was used to probe the structural change of lipid bilayers to investigate the hydrophobic mismatch between α-crystallins and lipid bilayers. Furthermore, ADH and insulin assays were used to monitor the chaperone activity of α-crystallins in the presence and absence of lipid bilayers. The result indicates the insertion of α-crystallins into lipid bilayers decreases their chaperone activity. We propose the observed hydrophobic mismatch could inhibit the insertion and release α-crystallins again to recover their chaperone activity.

Keywords: α-crystallin, lipid bilayers, hydrophobic mismatch, chaperone, lamellar X-ray diffraction (LXD)