Adapterin

Adapterin is a term that appears in some texts but is not a standard term in biochemistry or cell biology. In many cases it is a misspelling or informal variant of adaptin, or it is used as a generic label for adaptor proteins that bridge two or more molecular partners.

Adaptor proteins function as molecular bridges that bring enzymes, receptors, or other components into proximity, enabling processes such as signal transduction, endocytosis, or assembly of protein complexes. They are typically modular and may contain interaction domains (such as SH3, PDZ, or WW) and motifs that recognize specific cargo or receptor features. Because adaptor proteins can act in diverse pathways, their naming and classification can vary across literature.

The canonical term adaptin refers to a family of subunits that form adaptor protein (AP) complexes, which link cargo receptors to clathrin coats during vesicle formation. AP-1, AP-2, AP-3, AP-4, and AP-5 differ in tissue distribution and intracellular role, guiding vesicle trafficking between membranes. Each complex consists of multiple subunits (for example, AP-2 includes alpha, beta2, mu2, and sigma2) that coordinate cargo binding with interactions to clathrin and accessory proteins.

In practice, researchers addressing adaptor proteins should use adaptin or the specific adaptor protein name (for example, the AP-2 adaptor complex). If encountering the term "adapterin," treat it as a potential alias or nonstandard usage and verify with reliable sources.

See also: Adaptin; Adaptor protein; Clathrin-mediated endocytosis.