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Proc Natl Acad Sci U S A 1996 Feb 06;933:1282-6. doi: 10.1073/pnas.93.3.1282.
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A technique for detecting matrix proteins in the crystalline spicule of the sea urchin embryo.

Cho JW , Partin JS , Lennarz WJ .

The presence of proteins associated with the CaCO3-containing biocrystals found in a wide variety of marine organisms is well established. In these organisms, including the primitive skeleton (spicule) of the sea urchin embryo, the structural and functional role of these proteins either in the biomineralization process or in control of the structural features of the biocrystals is unclear. Recently, one of the matrix proteins of the sea urchin spicule, SM 30, has been shown to contain a carbohydrate chain (the 1223 epitope) that has been implicated in the process whereby Ca2+ is deposited as CaCo3. Because an understanding of the localization of this protein, as well as other proteins found within the spicule, is central to understanding their function, we undertook to develop methods to localize spicule matrix proteins in intact spicules, using immunogold techniques and scanning electron microscopy. Gold particles indicative of this matrix glycoprotein could not be detected on the surface of spicules that had been isolated from embryo homogenates and treated with alkaline hypochlorite to remove any associated membranous material. However, when isolated spicules were etched for 2 min with dilute acetic acid (10 mM) to expose more internal regions of the crystal, SM 30 and perhaps other proteins bearing the 1223 carbohydrate epitope were detected in the calcite matrix. These results, indicating that these two antigens are widely distributed in the spicule, suggest that this technique should be applicable to any matrix protein for which antibodies are available.

PubMed ID: 8577755
PMC ID: PMC40071
Article link: Proc Natl Acad Sci U S A

Genes referenced: LOC100887844
Antibodies: msp130 Ab4 sm30c Ab1

References [+] :
Aizenberg, Morphogenesis of calcitic sponge spicules: a role for specialized proteins interacting with growing crystals. 1995, Pubmed