This is a family of proteins conserved from plants to humans, in which two closely situated point mutations in the human protein lead to the condition of hereditary spastic paraplegia. Strumpellin contains one known domain called a spectrin repeat that consists of three alpha-helices of a characteristic length wrapped in a left-handed coiled coil. The spectrin proteins have multiple copies of this repeat, which can then form multimers in the cell. Spectrin associates with the cell membrane via spectrin repeats in the ankyrin protein. The spectrin repeat is a structural platform for cytoskeletal protein assemblies.