In-depth proteomic analysis of a mollusc shell: acid-soluble and acid-insoluble matrix of the limpet Lottia gigantea

Using three different sodium hypochlorite washing protocols before shell demineralization, a total of 569 proteins were identified in Lottia gigantea shell matrix. Of these, 311 were assembled in a consensus proteome comprising identifications contained in all proteomes irrespective of shell cleaning procedure. Some of these proteins were similar in amino acid sequence, amino acid composition, or domain structure to proteins identified previously in different bivalve or gastropod shells, such as BMSP, dermatopontin, nacrein, perlustrin, perlucin, or Pif. In addition there were dozens of previously uncharacterized proteins, many containing repeated short linear motifs or homorepeats. Such proteins may play a role in shell matrix construction or control of mineralization processes.The organic matrix of Lottia gigantea shells is a complex mixture of proteins comprising possible homologs of some previously characterized mollusc shell proteins, but also many novel proteins with a possible function in biomineralization as framework building blocks or as regulatory components. We hope that this data set, the most comprehensive available at present, will provide a platform for the further exploration of biomineralization processes in molluscs.Molluscan shells are extraordinarily stable biocomposites of calcium carbonate and an organic matrix consisting of polysaccharides and proteins. The organic matrix, although constituting a very minor fraction of the biocomposite by weight, is thought to be of utmost importance for the construction of the biocomposite and its final properties because it controls crystal nucleation, crystal growth, crystal shape and choice of calcium carbonate polymorph [1,2]. Previously established methods to identify new mollusc shell matrix proteins, such as isolation by chromatography and biochemical characterization or molecular biology approaches, have been complemented recently by mass spectrometry-based proteomic analysis or combination of proteo