Recombinant expression, purification and SAXS analysis of Arabidopsis thaliana ClpC1

• Published in: International journal of biological macromolecules 2021-01, Vol.167, p.1273-1280
• Main Authors: Jagdev, Manas Kumar, Dandapat, Jagneshwar, Vasudevan, Dileep
• Format: Article
• Language: English
• Subjects: Adenosine Triphosphate - chemistry; Amino Acid Sequence; Arabidopsis - chemistry; Arabidopsis - genetics; Arabidopsis - metabolism; Arabidopsis Proteins - chemistry; Arabidopsis Proteins - genetics; Arabidopsis Proteins - metabolism; Arabidopsis thaliana; Chloroplast Proteins - chemistry; Chloroplast Proteins - genetics; Chloroplast Proteins - metabolism; Chromatography, Gel; Circular Dichroism; Clp chaperone; ClpC1; Gene Expression; Heat-Shock Proteins - chemistry; Heat-Shock Proteins - genetics; Heat-Shock Proteins - metabolism; Hexameric conformation; Magnesium Chloride - chemistry; Phylogeny; Protein Domains; Protein Structure, Secondary; Purification; Recombinant Proteins - chemistry; Recombinant Proteins - genetics; Recombinant Proteins - isolation & purification; Recombinant Proteins - metabolism; Scattering, Small Angle; Small-angle X-ray scattering; X-Ray Diffraction
• ISSN: 0141-8130; 1879-0003
• DOI: 10.1016/j.ijbiomac.2020.11.081

Caseinolytic protease-associated chaperones (Clp chaperones) are HSP100 proteins belonging to the family of ATPases having diverse cellular functions, and they occur in various organisms ranging from bacteria to plants and mammals. Most Clp chaperones have a hexameric organization and associate with tetradecameric Clp proteases to recognize and unfold protein substrates that get degraded within the cellular milieu. Vascular plants have a diverse family of Clp chaperones compared to other organisms; wherein, the chloroplasts of Arabidopsis thaliana alone contain four distinct Clp chaperones, such as ClpC1, ClpC2, ClpD, and ClpB3. The paralogs AtClpC1 and AtClpC2 are more than 90% identical, though the extent of functional overlap between the two is not clear. Moreover, in vitro characterization reports are available only for AtClpC2, as AtClpC1 could not be expressed in recombinant form in the past. Herein, using a bacterial expression system, we have successfully expressed and purified AtClpC1 with a short N-terminal truncation, employing a three-step chromatographic purification strategy. We show that AtClpC1 exists as a hexamer in the presence of ATP and MgCl2, as known for other functional Clp chaperones. Further, our SAXS analyses provide a low-resolution envelope structure for the hexameric AtClpC1, which very well fits a ClpC hexamer model. •Clp chaperones act with proteases to recognize, unfold, and degrade protein substrates.•A. thaliana ClpC1 was expressed and purified using a bacterial expression system.•A three-step chromatographic strategy was used for purification.•Analytical SEC and SAXS show AtClpC1 to exist as a hexamer in solution.