A globular protein is a protein that is globe-like, or rounded in shape, often soluble in aqueous solution. This distinguishes them from fibrous proteins, such as keratin, which may not be all that soluble. The term is old, perhaps 19th century, predating the discovery of secondary structural motifs, and does not require the kinds of techniques used in modern structural biology. Something as simple as an ultracentrifuge can, via sedimentation coefficients, give useful information about a protein's globular nature.
Among the most known globular proteins is hemoglobin , a member of the globin protein family.
