Abstract
Chloride intracellular channels (CLICs) are a family of unique proteins, that were suggested to adopt both soluble and membrane-associated forms. Moreover, following this unusual metamorphic change, CLICs were shown to incorporate into membranes and mediate ion conduction in vitro, suggesting multimerization upon membrane insertion. Here, we present a 1.8 Å resolution crystal structure of the CLIC domain of mouse CLIC6 (mCLIC6). The structure reveals a monomeric arrangement and shows a high degree of structural conservation with other CLICs. Small-angle X-ray scattering (SAXS) analysis of mCLIC6 demonstrated that the overall solution structure is similar to the crystallographic conformation. Strikingly, further analysis of the SAXS data using ensemble optimization method unveiled additional elongated conformations, elucidating high structural plasticity as an inherent property of the protein. Moreover, structure-guided perturbation of the inter-domain interface by mutagenesis resulted in a population shift towards elongated conformations of mCLIC6. Additionally, we demonstrate that oxidative conditions induce an increase in mCLIC6 hydrophobicity along with mild oligomerization, which was enhanced by the presence of membrane mimetics. Together, these results provide mechanistic insights into the metamorphic nature of mCLIC6.
Highlights
The Chloride Intracellular Channel (CLIC) family forms a class of unusual and enigmatic intracellular proteins[1]
In order to gain molecular insights into the metamorphic nature of the canonical CLIC domain of mouse CLIC6, we purified and analyzed its conserved CLIC module. mCLIC6 was highly soluble in solution and crystallized using standard techniques
This unusual ability was attributed to a large conformational change within the canonical CLIC domain
Summary
The Chloride Intracellular Channel (CLIC) family forms a class of unusual and enigmatic intracellular proteins[1]. CLICs were surprisingly shown to exhibit unmediated association with artificial membranes, resulting in formation of ion conducting pores[6,9,10,11,12,13,14], as well as co-localize and interact with membrane proteins such as G protein coupled[15,16], and ryanodine receptors[17] These observations led to their classification as ‘metamorphic’ proteins[18]. Additional to the canonical GST-Ω class carboxy-terminal CLIC domain, CLIC6 endows a unique amino-terminal, predicted to be highly flexible, which exhibits poor sequence similarity to any known protein. We show that mCLIC6 undergoes a conformational change and oligomerization that depends on both oxidative conditions and the presence of lipids
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
