(Weiss et al. 2001), Perlwapin with an acidic protein domain (Treccani et al. 2006),
and Perlucin containing a C-type functional lectin domain (Weiss et al. 2000).
Perlucin is able to nucleate calcium carbonate on calcite, and to be occluded into
calcium carbonate crystals as an intracrystalline protein (Blank et al. 2003).
Perlinhibin induces the formation of aragonite on calcite substrate by inhibiting
the growth of calcite crystals (Mann et al. 2007), whereas Perlwapin inhibits the
growth of certain crystallographic planes in the mineral phase of nacre (Treccani
et al.2006).
Lustrin A is the largest protein found in the aragonite layer of abalone shell,
identified from Haliotis rufescens by screening the mantle cDNA library (Shen
et al. 1997), with a high proportion of Ser, Pro, Gly, and Cys. Having a protease
inhibitor-like domain and a similar extracellular matrix domain, Lustrin A is
thought to be a multifunctional protein. Its 24AA Asp-rich (D4) sequence domain
influences crystal growth in a concentration-dependent manner during in vitro
mineralization (Wustman et al. 2003).
12.4 Function of Matrix Proteins
Generally, at least five strategies are used to study the functions of matrix proteins:
(1) Analyzing in situ hybridization to display the gene expression characteristics in
different mantle regions that are known to secrete components to form shell
(Lowenstam and Weiner 1989). Genes encoding nacreous matrix proteins are
preferentially expressed in more dorsal regions of the mantle (Sudo et al. 1997;
Takeuchi and Endo 2006) where outer epithelia have a high proliferation rate (Fang
et al. 2008), whereas genes encoding prismatic ones usually are expressed in the
edge of the mantle (Takeuchi and Endo 2006). (2) Cloning the genes encoding
matrix proteins, from which the complete amino acid sequence and the secondary
structure are deduced. Based on this information, the proteins’ functions involved
in nacre biomineralization are speculated. (3) Using in vitro calcium carbonate
crystallization experiments to study the effect of native nacreous matrix proteins
(Yan et al. 2007), recombinant ones, or synthesized functional polypeptides
(Michenfelder et al. 2003; Kim et al. 2006; Evans 2008) from these proteins, on
aragonitic crystals formation and growth; (4) Mapping the distribution of organic
matrix proteins or their components on the surface of interlamellar matrices from
nacreous layer of shell using immunohistochemical or immunofluorescence
methods (Addadi et al. 2006; Nudelman et al. 2006; Bezares et al. 2008), their
presence at the location is usually consistent with their supposed role in nacre
formation. (5) Knocking out the genes encoding matrix proteins by RNA interference (Suzuki et al. 2009), or restraining the physiological functions of these
proteins by injecting the antibodies against them into the extrapallial space (Ma
et al. 2007; Gong et al. 2008c; Kong et al. 2009), then checking the formation of the
nacreous layer of shell in vivo by SEM. Therefore, the functions of proteins in nacre
12 Molecular Approaches to Understand Biomineralization of Shell Nacreous Layer
341
and Perlucin containing a C-type functional lectin domain (Weiss et al. 2000).
Perlucin is able to nucleate calcium carbonate on calcite, and to be occluded into
calcium carbonate crystals as an intracrystalline protein (Blank et al. 2003).
Perlinhibin induces the formation of aragonite on calcite substrate by inhibiting
the growth of calcite crystals (Mann et al. 2007), whereas Perlwapin inhibits the
growth of certain crystallographic planes in the mineral phase of nacre (Treccani
et al.2006).
Lustrin A is the largest protein found in the aragonite layer of abalone shell,
identified from Haliotis rufescens by screening the mantle cDNA library (Shen
et al. 1997), with a high proportion of Ser, Pro, Gly, and Cys. Having a protease
inhibitor-like domain and a similar extracellular matrix domain, Lustrin A is
thought to be a multifunctional protein. Its 24AA Asp-rich (D4) sequence domain
influences crystal growth in a concentration-dependent manner during in vitro
mineralization (Wustman et al. 2003).
12.4 Function of Matrix Proteins
Generally, at least five strategies are used to study the functions of matrix proteins:
(1) Analyzing in situ hybridization to display the gene expression characteristics in
different mantle regions that are known to secrete components to form shell
(Lowenstam and Weiner 1989). Genes encoding nacreous matrix proteins are
preferentially expressed in more dorsal regions of the mantle (Sudo et al. 1997;
Takeuchi and Endo 2006) where outer epithelia have a high proliferation rate (Fang
et al. 2008), whereas genes encoding prismatic ones usually are expressed in the
edge of the mantle (Takeuchi and Endo 2006). (2) Cloning the genes encoding
matrix proteins, from which the complete amino acid sequence and the secondary
structure are deduced. Based on this information, the proteins’ functions involved
in nacre biomineralization are speculated. (3) Using in vitro calcium carbonate
crystallization experiments to study the effect of native nacreous matrix proteins
(Yan et al. 2007), recombinant ones, or synthesized functional polypeptides
(Michenfelder et al. 2003; Kim et al. 2006; Evans 2008) from these proteins, on
aragonitic crystals formation and growth; (4) Mapping the distribution of organic
matrix proteins or their components on the surface of interlamellar matrices from
nacreous layer of shell using immunohistochemical or immunofluorescence
methods (Addadi et al. 2006; Nudelman et al. 2006; Bezares et al. 2008), their
presence at the location is usually consistent with their supposed role in nacre
formation. (5) Knocking out the genes encoding matrix proteins by RNA interference (Suzuki et al. 2009), or restraining the physiological functions of these
proteins by injecting the antibodies against them into the extrapallial space (Ma
et al. 2007; Gong et al. 2008c; Kong et al. 2009), then checking the formation of the
nacreous layer of shell in vivo by SEM. Therefore, the functions of proteins in nacre
12 Molecular Approaches to Understand Biomineralization of Shell Nacreous Layer
341