Analysis of the interactions of Tafazzin and Beta-2 Glycoprotein I with lipid membrane by hydrogen/deuterium exchange mass spectrometry

• Main Authors: WU, TING-YUAN, 吳庭遠
• Other Authors: HSU,YUAN-HAO
• Format: Others
• Language: zh-TW
• Published: 2018
• Online Access: http://ndltd.ncl.edu.tw/handle/uqu7b2

碩士 === 東海大學 === 化學系 === 106 === Hydrogen/deuterium exchange (HDX) coupled with mass spectrometry (ESI-MS) has been widely used to study the mechanisms of protein dynamics, domain structure, protein-ligand interactions and protein conformational changes. Beta 2 Glycoprotein I (β2GPI) is a membrane protein and it was discovered to be the major antigen for the antiphospholipid antibodies(aPL Abs) in the antiphospholipid syndrome. The β2GPI complex binds with antibody will interact with some receptors, such as annexin A2, TLR family, glycoprotein Ibα, LRP8 to induce inflammation and prothrombotic. Many studies have suggested that β2GPI is not recognized by aPL Abs in the blood circulation. When negatively charged protein surface become exposed, the domain V of β2GPI will bind to the surface and change conformation. Then the aPL Abs are able to recognize the epitope in domain I of β2GPI. Here, we prepared 1,2-dioleoyl-sn-glycero-3-phospho-L-serine(18:1DOPS) and cardiolipin (CL) vesicles to simulate anion surface membrane. The interactions of the β2GPI with the anion membrane vesicles were analyzed by hydrogen/deuterium exchange mass spectrometry (HDXMS). The exchange level of sequence 21-27 significantly increased after β2GPI interacted with DOPS for 10 min. This results indicated that the interaction between domain I and domain V decreased, which caused the sequence 21-27 protruding out of the circular shape of the protein structure. β2GPI still maintained the circular conformation while interacting with DOPS. The exchange levels of the highly accessible sequences 1-20, 53-77, 175-188, 259-268 and 294-306 slightly decreased due to the nonspecific adsorption between β2GPI and DOPS by electrostatic force and hydrogen bonds. After β2GPI interacted with CL 10 mins. The exchange amount of sequence 21-27 significantly increased. This result was same with DOPS, suggesting the perturbation of sequence 21-27 is a preliminary behavior caused by the phospholipid binding. After β2GPI interacted with CL for 30 min, the exchange levels in several sequences significantly increased, including 1-20, 21-27, 41-51, 70-86, 153-162, 191-198, 196-205, 273-279, 297-306 and 310-316.The increasing of 1-20, 21-27, 41-51, 297-306 and 310-316 indicated that domain I did not interact with domain V and these sequences have been exposed. The increasing deuteration levels in 70-86, 153-162, 191-198, 196-205 and 273-279 indicated β2GPI conformation changed from ring conformation to chain conformation, leading to the exposure of the inner region. Overall, β2GPI could not change the ring conformation while initial contact with lipid membrane, but sequence 21-27 will be exposed. β2GPI continued to drastically change its conformation from ring to chain conformation while staying on the lipid membrane surface.