title: Proteomic analysis of the acid-soluble nacre matrix of the bivalve Unio pictorum: detection of novel carbonic anhydrase and putative protease inhibitor proteins.
abstract: The matrix extracted from mollusc shell nacre is a mixture of proteins and glycoproteins that is thought to play a major role in controlling biomineral synthesis and in increasing its mechanical properties. We investigated the nacreous shell of the freshwater mussel Unio pictorum, to which we applied a proteomics approach adapted to mollusc shell proteins. On one hand, the acid-soluble nacre matrix was fractionated by SDS-PAGE and the five main protein bands (P95, P50, P29, P16, and P12) were digested with trypsin and analyzed by nanoLC-MS/MS followed by de novo sequencing. On the other hand, the acid-soluble nacre matrix was analyzed in a similar manner, without any preliminary fractionation. In total, we obtained about 140 peptides, of between 9 and 21 residues, as well as several shorter peptides. Interestingly, it appears that the different protein bands share several identical peptides; this has implications for the underlying genetic machinery that synthesizes nacre proteins. Homology searches against sequences in the Swiss-Prot protein database and the 800,000 mollusc expressed sequence tag database were performed, but surprisingly, only a few obvious homologies were established. Among the peptides that match with known sequences, some from P50 and P16/P12 proteins align with carbonic anhydrase (CA) and with the protease inhibitor, respectively. The evolutionary implications of our findings are discussed.
authors.affiliation: UMR 5561 CNRS Biogéosciences, Université de Bourgogne, 21000 Dijon, France. benjamin.marie@u-bourgogne.fr
authors.forename: Benjamin
authors.initials: B
authors.lastname: Marie
authors.forename: Isabelle
authors.initials: I
authors.lastname: Zanella-Cléon
authors.forename: Nathalie
authors.initials: N
authors.lastname: Le Roy
authors.forename: Michel
authors.initials: M
authors.lastname: Becchi
authors.forename: Gilles
authors.initials: G
authors.lastname: Luquet
authors.forename: Frédéric
authors.initials: F
authors.lastname: Marin
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002256:Carbonic Anhydrases / Q000737:chemistry* / Q000378:metabolism; D002853:Chromatography, Liquid; D030562:Databases, Protein; D008969:Molecular Sequence Data; D011480:Protease Inhibitors / Q000737:chemistry*; D020543:Proteome / Q000032:analysis*; D020539:Sequence Analysis, Protein; D021241:Spectrometry, Mass, Electrospray Ionization; D049881:Unio / Q000201:enzymology*
chemical_list: D011480:Protease Inhibitors; D020543:Proteome; D002256:Carbonic Anhydrases