Báo cáo khoa học: The shell matrix of the freshwater mussel Unio pictorum (Paleoheterodonta, Unionoida) Involvement of acidic polysaccharides from glycoproteins in nacre mineralization

The Shell Matrix of the Freshwater Mussel Unio Pictorum (Paleoheterodonta, Unionoida): Involvement of Acidic Polysaccharides from Glycoproteins in Nacre Mineralization

Authors: Benjamin Marie, Gilles Luquet, Jean-Paul Pais De Barros, Nathalie Guichard, Sylvain Morel, Gérard Alcaraz, Loïc Bollache and Frédéric Marin

Field: Biomineralization, Glycoproteins, Nacre Mineralization

Document Summary: This study investigates the biochemical properties of the aragonitic shell matrix of the freshwater bivalve Unio pictorum. Analysis of the acid-soluble and acid-insoluble fractions revealed distinct amino acid and monosaccharide compositions. Electrophoretic analysis identified three major polyanionic calcium-binding glycoproteins (P95, P50, and P29) in the acid-soluble matrix. Chemical deglycosylation significantly altered the molecular mass and isoelectric points of these proteins, affecting CaCO₃ crystal growth and calcium-binding ability. The findings highlight the crucial role of post-translational modifications, particularly glycosylation, in mollusc shell calcification. The study also explores the influence of the shell matrix on calcite crystal formation and suggests that saccharidic moieties are integral to the inhibition of crystal growth and potentially involved in other biomineralization processes.

Detailed Table of Contents:

• Keywords
• Correspondence
• Abbreviations
• Abstract
• Introduction
• Results
• Discussion
• Experimental procedures
• Shell material
• Shell preparation and matrix extraction
• ASM and AIM analysis on mono-dimensional SDS/PAGE
• Infrared analysis on ASM and AIM
• Amino acid composition of ASM and AIM
• Monosaccharide analysis of ASM and AIM
• Spectrophotometric determination of sulfated carbohydrates
• ASM polysaccharide staining and ASM calcium-binding ability on gels
• In vitro inhibition of calcium carbonate precipitation by the ASM
• ASM deglycosylation studies
• ASM analysis on 2D gel electrophoresis
• Growth of calcite crystals in the presence of native and chemically deglycosylated ASM
• Acknowledgements
• References