Xenopus laevis egg jelly coats consist of small diffusible proteins bound to a complex system of structurally stable networks composed of high-molecular-weight glycoconjugates.
The extracellular matrix surrounding Xenopus laevis eggs includes three morphologically distinct jelly layers designated J1, J2, and J3 from the innermost to outermost. Previously, using the quick-freeze, deep-etch, rotary-shadow technique, we found that each layer has a unique fibrillogranular ultrastructure. In this study, we show that the fibrillar network is composed of high-molecular-weight glycoconjugates, while the globular material consists of low-molecular-weight proteins some of which are released into the aqueous medium. Analysis by SDS-PAGE and differential staining of individually dissected jelly layers shows that both J1 and J2 contain three high-molecular-weight, acidic, Alcian blue-straining components (450, 630, and 900 kDa), while J3 contains two high-molecular-weight components that strain with PAS but not with Alcian blue. Each jelly layer also contains low-molecular-weight proteins from 75 to 250 kDa that do not stain with PAS or Alcian blue. Chromatography of whole egg jelly on a Sephacryl 500 column resulted in isolation of the major Alcian blue staining band (630 kDa) which eluted first, and two PAS staining bands which eluted second. Rotary-shadowing demonstrated that these high-molecular-weight glycoconjugates are long and branched, suggesting that they are major constituents of the jelly fiber network. SDS-PAGE analysis shows that these networks are stable for at least 16 hr after eggs are oviposited. In contrast, the low-molecular-weight globular proteins which constitute 30% of the total jelly protein are steadily released into the surrounding medium.
Bonnell
B S
BS
Department of Zoology, Arizona State University, Tempe, Arizona 85287-1501, USA.
Reinhart
D
D
Chandler
D E
DE
D000818:Animals; D004058:Diffusion; D004591:Electrophoresis, Polyacrylamide Gel; D005109:Extracellular Matrix / Q000737:chemistry; D016326:Extracellular Matrix Proteins / Q000737:chemistry; D005260:Female; D005613:Freeze Etching; D006001:Glycoconjugates / Q000737:chemistry; D006023:Glycoproteins / Q000737:chemistry; D006801:Humans; D008970:Molecular Weight; D010063:Ovum / Q000737:chemistry* / Q000648:ultrastructure*; D014982:Xenopus laevis
D016326:Extracellular Matrix Proteins; D006001:Glycoconjugates; D006023:Glycoproteins