Molecular calcium-binding chaperone promoting folding, oligomeric assembly and quality control in the ER via the calreticulin/calnexin cycle. This lectin may interact transiently with almost all of the monoglucosylated glycoproteins that are synthesized in the ER (By similarity). Monomer. Expressed in fat bodies. Not expressed in midgut, silk gland, ovary or testis. Induced by disturbances in intracellular calcium levels caused by the chelators BAPTA-AM and EDTA, the endoplasmic reticulum calcium-ATPase inhibitor thapsigargin and by calcium. Not induced by the endoplasmic reticulum stress-inducing drugs brefeldin A, DTT and tunicamycin, or by heat stress and hydrogen peroxide. Can be divided into a N-terminal globular domain, a proline-rich P-domain forming an elongated arm-like structure and a C-terminal acidic domain. The P-domain binds one molecule of calcium with high affinity, whereas the acidic C-domain binds multiple calcium ions with low affinity (By similarity). The interaction with glycans occurs through a binding site in the globular lectin domain. The zinc binding sites are localized to the N-domain. Belongs to the calreticulin family.