Proteins and surfactants coexist in biological and industrial systems, and have the potential to interact due to electrostatic, steric and hydrophobic interactions. As a result, protein molecules may alter the interfacial energy of surfactant monolayers, and thereby modify the phase behavior of surfactants. It is particularly interesting to study self-assembly in equivolume mixtures of oil and water, in which the surfactant is free to form various nanostructures, depending on the spontaneous curvature of the monolayer. Using SAXS, we have found that small amounts of the water-soluble, globular protein alpha-lactalbumin markedly alter phase morphologies of the surfactant AOT: transforming spherical water-in-oil (w/o) microemulsion droplets to large w/o ellipsoids, to inverted oil-in-water droplets, and to liquid crystalline and gel-forming structures. As the protein to surfactant ratio increases, the aspect ratio of the structures also increases, and self-assembly shifts from the organic to aqueous phase. In the presence of the protein these morphologies are tuned by protein charge and ionic strength, with the protein/surfactant interaction now apparently controlling the self-assembly. More subtle effects of protein on phospholipid self-assembly are also observed, and suggest a significant role for molecular architecture.