title: The structure-function relationship of MSI7, a matrix protein from pearl oyster Pinctada fucata.
abstract: We previously identified a matrix protein, MSI7, from pearl oyster Pinctada fucata. According to the structural analysis, the DGD site in the N-terminal of MSI7 is crucial for its role in the shell formation. In this study, we expressed a series of recombinant MSI7 proteins, including the wild-type and several mutants directed at the DGD site, using an Escherichia coli expression system to reveal the structure-function relationship of MSI7. Furthermore, in vitro crystallization, crystallization speed assay, and circular dichroism spectrometry were carried out. Results indicated that wild-type MSI7 could induce the nucleation of aragonite and inhibit the crystallization of calcite. However, none of the mutants could induce the nucleation of aragonite, but all of them could inhibit the crystallization of calcite to some extent. And all the proteins accelerated the crystallization process. Taken together, the results indicated that MSI7 could contribute to aragonite crystallization by inducing the nucleation of aragonite and inhibiting the crystallization of calcite, which agrees with our prediction about its role in the nacreous layer formation of the shell. The DGD site was critical for the induction of the nucleation of aragonite.
authors.affiliation: Department of Biological Science and Biotechnology, Institute of Marine Biotechnology, Tsinghua University, Beijing 100084, China.
authors.forename: Qiaoli
authors.initials: Q
authors.lastname: Feng
authors.forename: Zi
authors.initials: Z
authors.lastname: Fang
authors.forename: Zhenguang
authors.initials: Z
authors.lastname: Yan
authors.forename: Rui
authors.initials: R
authors.lastname: Xing
authors.forename: Liping
authors.initials: L
authors.lastname: Xie
authors.forename: Rongqing
authors.initials: R
authors.lastname: Zhang
mesh_terms: D000818:Animals; D001665:Binding Sites; D002119:Calcium Carbonate / Q000737:chemistry*; D002621:Chemistry; D016326:Extracellular Matrix Proteins / Q000737:chemistry* / Q000378:metabolism / Q000648:ultrastructure*; D010125:Ostreidae / Q000378:metabolism*; D011485:Protein Binding; D011487:Protein Conformation; D013329:Structure-Activity Relationship
chemical_list: D016326:Extracellular Matrix Proteins; D002119:Calcium Carbonate