Mouse Calreticulin (aa 24-43) Synthetic Peptide. Calr or Calreticulin is a calcium-binding chaperone that promotes folding, oligomeric assembly and quality control in the endoplasmic reticulum (ER) via the calreticulin/calnexin cycle. Calr, a lectin, interacts transiently with almost all of the monoglucosylated glycoproteins that are synthesized in the ER. Calr also interacts with with the DNA-binding domain of NR3C1 and mediates its nuclear export. It may also be involved in maternal gene expression regulation and oocyte maturation via the regulation of calcium homeostasis.