Nacre evolution: A proteomic approach
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Nacre evolution: a proteomic approach Benjamin MARIE1, Nathalie LE ROY1, Arul MARIE2, Lionel DUBOST2, Christian MILET3, Laurent BEDOUET3, Michel BECCHI4, Isabelle ZANELLA-CLEON4, Daniel JACKSON5, Bernard DEGNAN5, Gilles LUQUET1 and Frédéric MARIN1 1
UMR 5561 CNRS, Biogeosciences, Université de Bourgogne, 6 Bd. Gabriel F-21000, France e-mail: [email protected]; [email protected] 2 Département RDDM, Plateforme de Spectrométrie de Masse et de Protéomique, MNHN, 75231 Paris, France 3 UMR CNRS 5178, Biologie des Organismes Marins et Ecosystèmes, MNHN, 75231 Paris, France 4 UMR 5086 CNRS, Institut de Biologie et de Chimie des Protéines (IBCP), 69367 Lyon, France 5 School of Integrative Biology, University of Queensland, 4072 Queensland, Australia
ABSTRACT From an evolutionary viewpoint, the molluscan nacre constitutes a fascinating object. This microstructure appeared early, in the Lower Cambrian period, about 530 million years ago, and since then, has been kept unchanged until today. Nacre is restricted to the conchiferan mollusks, where it occurs in t least three main classes, bivalves, gastropods and cephalopods. The aim of the present study is to investigate whether all nacres are built from the same “macromolecular tools”, proteins of the nacre matrix. To this end, we studied three new nacre models, the freshwater bivalve Unio pictorum, the cephalopod Nautilus macromphalus, and the gastropod Haliotis asinina, to which we applied a combined biochemical and proteomic characterization of their respective nacre matrices. The results of our approach, that can be defined as “shellomics” (proteomics applied to shell proteins) shed a new light on the macroevolution of nacre matrix proteins and on the in vitro design of nacrelike biomaterials.
INTRODUCTION Because of its exceptional toughness, of its commercial value in jewelry, of its remarkable biocompatibility properties when implanted in vivo, nacre is by far the most studied molluscan shell microstructure [1] and many authors consider it as the reference model for understanding at the micro and nano scales how molluscs control the regular deposition of calcium carbonate tablets [2]. On a structural viewpoint, nacre consists of a regular superimposition of polygonal flat aragonitic tablets of 0.5-µm thick, embedded in a peripheral thin organic matrix [3]. Biochemical characterizations, mainly performed on two models, the pearl oyster Pinctada sp. and the abalone Haliotis sp., have shown that the nacre matrix comprises a large set of macromolecular components including chitin, hydrophobic ‘framework’ proteins and several soluble proteins and glycoproteins [4]. The nacre appeared early in the fossil record, somewhere in the Cambrian period [5]. Since then, it has been kept almost unchanged throughout the Phanerozoic time. Nacre is represented in at least three classes, bivalves, gastropods and cephalopods. In monoplacophorans, true nacre is only observed in one extant genus [6]. Taking into
consideration the phylogenetic tree shown
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