Isolation and characterization of a component of the surface sheath of Dictyostelium discoideum.

Aggregates of Dictyostelium discoideum are surrounded by a surface sheath which functions to maintain polarity and integrity during development. We have isolated and partially characterized a component of the surface sheath. It is composed of 60% cellulose, 15% protein, 3% heteropolysaccharide (heteropolymer), 5% lipid, and 1% sulfate when isolated from migrating slugs. The sheath, isolated from aggregates prior to tip formation, has less protein, a different heteropolymer, and cellulose of a lower crystallinity than the sheath of migrating slugs. The increase in crystallinity of the cellulose during development may be important in determining the strength of the surface sheath.