Fesselin is a natively unfolded protein.

Fesselin is a heat stable proline-rich actin binding protein. The stability, amino acid composition, and ability to bind to several proteins suggested that fesselin may be unfolded under native conditions. While the complete sequence of fesselin is unknown an analysis of a closely related protein, synaptopodin 2 from Gallus gallus, indicates that fesselin consists of a series of unstructured regions interspersed between short folded regions.