Lectins are carbohydrate-binding proteins, macromolecules that are highly specific for sugar moieties of other molecules. Lectins perform recognition on the cellular and molecular level and play numerous roles in biological recognition phenomena involving cells, carbohydrates, and proteins. Lectins also mediate attachment and binding of bacteria and viruses to their intended targets.
Lectins are ubiquitous in nature and are found in many foods. Some foods such as beans and grains need to be cooked or fermented to reduce lectin content. Some lectins are beneficial, such as CLEC11A which promotes bone growth, while others may be powerful toxins such as ricin.Lectins may be disabled by specific mono- and oligosaccharides, which bind to ingested lectins from grains, legume, nightshade plants and dairy; binding can prevent their attachment to the carbohydrates within the cell membrane. The selectivity of lectins means that they are very useful for analyzing blood type, and they are also used in some genetically engineered crops to transfer traits, such as resistance to pests and resistance to herbicides.