An alpha solenoid is a protein fold found in the protein subunits of light-harvesting complexes, particularly in the peridinin chlorophyll proteins of dinoflagellates, and as domains of larger eukaryotic proteins that make up the nuclear pore complex. The fold consists of alpha helices arranged in a curved pattern that resembles a jelly roll fold. The extent of an alpha solenoid's curvature depends on the primary sequence; strongly curved solenoids have predictable sequence patterns and have led to the identification of probable solenoid-like components in the proteasome.