spectrinrepeat

A spectrin repeat is a conserved protein domain found in the spectrin family of cytoskeletal proteins and in a broader set of cytoskeletal and signaling proteins. Each repeat is about 100 amino acids in length and typically forms a three-helix bundle. Repeats are commonly assembled in tandem, creating long, flexible rod-like regions that can span substantial distances within a protein.

Structurally, a spectrin repeat consists of three alpha-helices arranged to form a compact, left-handed bundle. The repeats stack to produce elongated architectures, with flexible linkers between repeats allowing bending and extension. The modular nature of the domain enables proteins to adapt their length and mechanical properties by varying the number of repeats.

Spectrin repeats occur throughout the spectrin superfamily, including classical spectrin proteins, dystrophin and utrophin, plakins (such as plectin and BPAG1), and various nesprins and related cytoskeletal adapters. These domains often serve as scaffolds for protein-protein interactions, linking the actin cytoskeleton to membrane components and other structural or signaling partners.

Functionally, spectrin repeats contribute to cellular mechanics by providing elasticity and resilience to membranes and cytoskeletal networks. They also help organize signaling complexes through their interaction surfaces, coordinating processes such as membrane stabilization, force transmission, and spatial organization of proteins at specific cellular sites.

Mutations or disruptions affecting spectrin repeats can perturb cytoskeletal architecture and are associated with a range of diseases, including red blood cell membrane disorders and muscular or connective tissue pathologies, depending on the protein context.