[대학원 생명과학과 세미나 안내]
연사 : 임현호 박사 (한국뇌연구원)
연제 : Structure-function of the coupled ion transport in a CLC antiporter
일시 : 2020년 6월 5일 (금) 오후 5시
장소 : 온라인 화상 강의로 진행됩니다.
초청교수 : 우재성 교수
Abstract
The CLC family proteins are involved in a variety of physiological processes to control cellular chloride concentration. Two distinct classes of CLC proteins, Cl- channels and Cl-/H+ antiporters, have been functionally and structurally investigated over the last several decades. Previous studies have suggested that the conformational heterogeneity of the critical glutamate residue, Gluex, could explain the transport cycle of CLC-type Cl-/H+ antiporters. However, the presence of multiple conformations (Up, Middle, and Down) of the Gluex has been suggested from combined structural snapshots of two different CLC antiporters: CLC-ec1 from Escherichia coli and cmCLC from athermophilic red alga, Cyanidioschyzonmerolae. Thus, we aimed to investigate the heterogeneity of Gluex-conformations in CLC-ec1, the most deeply studied CLC antiporter, at both functional andstructural levels. Here, we show that the crystal structures of the Gluex mutant, E148D and wild-type CLC-ec1 with varying anion concentrations suggest a new structural intermediate, the “Mid-low” conformation. We also found that an extra anion can be located above the external Cl—binding site in the E148D mutant when the anion concentration is high. Moreover, we observed that a carboxylate in solution can occupy either the external or central Cl—binding site in the ungated E148A mutant using an anomalously detectable short carboxylic acid, bromoacetate. These results lend credibility to the idea that the Gluex can take at least three distinct conformational states during the transport cycle of a single CLC antiporter.