Calcium-binding protein that interacts with newly synthesized monoglucosylated glycoproteins in the endoplasmic reticulum. It may act in assisting protein assembly and/or in the retention within the ER of unassembled protein subunits. It seems to play a major role in the quality control apparatus of the ER by the retention of incorrectly folded proteins. Associated with partial T-cell antigen receptor complexes that escape the ER of immature thymocytes, it may function as a signaling complex regulating thymocyte maturation. Additionally it may play a role in receptor-mediated endocytosis at the synapse. Interacts with MAPK3/ERK1 (By similarity). Interacts with KCNH2 (PubMed:16361248). Associates with ribosomes (By similarity). Interacts with SGIP1; involved in negative regulation of endocytosis (By similarity). The palmitoylated form interacts with the ribosome-translocon complex component SSR1, promoting efficient folding of glycoproteins (PubMed:22314232). Interacts with SERPINA2P/SERPINA2 and with the S and Z variants of SERPINA1 (PubMed:23826168). Interacts with PPIB (PubMed:20801878). Interacts with ZNRF4 (PubMed:21205830). Interacts with SMIM22 (PubMed:29765154). Interacts with TMX2 (PubMed:31735293). Interacts with TMEM35A/NACHO (By similarity). Interacts with CHRNA7 (PubMed:32783947). (Microbial infection) Interacts with HBV large envelope protein, isoform L. (Microbial infection) Interacts with HBV large envelope protein, isoform M; this association may be essential for isoform M proper secretion. Identified by mass spectrometry in melanosome fractions from stage I to stage IV (PubMed:12643545, PubMed:17081065). The palmitoylated form preferentially localizes to the perinuclear rough ER (PubMed:22314232). Phosphorylated at Ser-564 by MAPK3/ERK1. phosphorylation by MAPK3/ERK1 increases its association with ribosomes (By similarity). Palmitoylation by DHHC6 leads to the preferential localization to the perinuclear rough ER. It mediates the association of calnexin with the ribosome-translocon complex (RTC) which is required for efficient folding of glycosylated proteins. Ubiquitinated, leading to proteasomal degradation. Probably ubiquitinated by ZNRF4. Belongs to the calreticulin family. Calnexin entry