Conformation and stability of arginylated calreticulin

DECCA M.B.; CARPIO M.; DURAND S.; HALLAK M.; MONTICH G.

Salta

Congreso; XXXIX Annual Meeting of the Argentinean Biophysical Society, Workshop CeBEM and Latin American Protein Society Meeting; 2010

Argentinean Biophysical Society, CeBEM and Latin American Protein Society

Calreticulin (CRT) is a multifunctional Ca2+-binding protein involved in a variety of cellular processes. The main cellular location of CRT is the ER, but it had been also localized in the cytoplasm, the nucleus, and on the cell membrane. CRT has a dynamic structure, capable of acquire different conformations depending of the environmental conditions. Conformational flexibility of CRT seems to be a key point in regulating the diverse function of this protein.We recently found that CRT can be post translationally modified by the covalent addition of arginine in its terminal end. The reaction is catalyzed by the ATE enzyme in the cytoplasm in conditions that favor a more expanded CRT tertiary structure. It is likely that arginylation further modulate the CRT functions since, for example, is essential for the recruitment of CRT to stress granules under several stress conditions.The aim of this study was to investigate the conformation and stability of CRT upon arginylation. Global protein secondary structure of CRT was assessed by FTIR. Amide I' band deconvolution shows components corresponding to alfa-helices, beta-sheets and unordered structures. A slight increment in alfa-helix content and unordered structures were found in the arginylated protein, as well as a higher tendency to form intermolecular aggregates at high temperatures. Differential Scanning Calorimetry indicates that, at high calcium concentration, CRT arginylation produces only marginal decrease in protein thermal stability. On the other hand, in conditions of complete calcium depletion, the arginilated CRT has a less cooperative thermal denaturation and a lower onset temperature in comparison with the non arginylated protein.This work was supported by grants from FONCyT, CONICET and SECyT-UNC