Characterization on organic matrix proteins enclosed in high Mg-calcite crystals of the coralline sponge Spirastrella (Acanthochaetetes) wellsi

Abstract

Protein components found in freeze-dried specimens of the coralline sponge Spirastrella (Acanthochaetetes) wellsi were separated and characterized . Proteins extracted from skeleton crystals (matrix proteins) contained high concentrations of glycin (16 %) as weil as enhanced amounts of asparagin/aspartic acid (11 %) and glutamin/glutamic acid (10 %). At least 10 proteins could be separated by SDSPAGE. Six of them, with molecular weights between 30 and 45 kDa, may be considered as distinct matrix proteins. The bulk of total soluble proteins as weil as all soluble matrix proteins are acidic with pH values below 5. Our results indicate that at least in one stage crystal growth is matrix mediated, i.e. controlled by the sponge.