Galectin-3 contains a carboxyl-terminal lectin domain and an amino-terminal non-lectin part consisting primarily of short tandem repeats. It is widely distributed in tissues and found in epithelial cells, fibroblasts, dendritic cells, and inflammatory cells.
In many cell types studied, galectin-3 is present diffusely in the cytoplasm, but is also localized to the nucleus and subcellular structures, such as mitochondria, phagosomes and exosomes, under specific conditions. It is secreted by various cell types, including monocytes, macrophages, and epithelial cells, and the extracellular protein can bind to a large number of different glycoconjugates on the cell surfaces and extracellular matrices.