Internalins are surface proteins found on Listeria monocytogenes. They exist in two known forms, InlA and InlB. They are used by the bacteria to invade mammalian cells via cadherins

Cadherin

Cadherins are a class of type-1 transmembrane proteins. They play important roles in cell adhesion, ensuring that cells within tissues are bound together. They are dependent on calcium ions to function, hence their name.The cadherin superfamily includes cadherins, protocadherins, desmogleins, and...

transmembrane proteins. The exact role of these proteins and their invasiveness in vivo is not completely understood. In cultured cells, InlA is necessary to facilitate Listeria entry into human epithelial cells. While InlB is necessary for Listeria internalisation in several other cell types, including hepatocytes, fibroblasts, and epithelioid cells.