title: Novel basic protein, PfN23, functions as key macromolecule during nacre formation.
abstract: The fine microstructure of nacre (mother of pearl) illustrates the beauty of nature. Proteins found in nacre were believed to be "natural hands" that control nacre formation. In the classical view of nacre formation, nucleation of the main minerals, calcium carbonate, is induced on and by the acidic proteins in nacre. However, the basic proteins were not expected to be components of nacre. Here, we reported that a novel basic protein, PfN23, was a key accelerator in the control over crystal growth in nacre. The expression profile, in situ immunostaining, and in vitro immunodetection assays showed that PfN23 was localized within calcium carbonate crystals in the nacre. Knocking down the expression of PfN23 in adults via double-stranded RNA injection led to a disordered nacre surface in adults. Blocking the translation of PfN23 in embryos using morpholino oligomers led to the arrest of larval development. The in vitro crystallization assay showed that PfN23 increases the rate of calcium carbonate deposition and induced the formation of aragonite crystals with characteristics close to nacre. In addition, we constructed the peptides and truncations of different regions of this protein and found that the positively charged C-terminal region was a key region for the function of PfN23 Taken together, the basic protein PfN23 may be a key accelerator in the control of crystal growth in nacre. This provides a valuable balance to the classic view that acidic proteins control calcium carbonate deposition in nacre.
authors.affiliation: Institute of Marine Biotechnology, School of Life Sciences, Tsinghua University, Beijing 100084, China.
authors.forename: Dong
authors.initials: D
authors.lastname: Fang
authors.forename: Cong
authors.initials: C
authors.lastname: Pan
authors.forename: Huijuan
authors.initials: H
authors.lastname: Lin
authors.forename: Ya
authors.initials: Y
authors.lastname: Lin
authors.forename: Guiyou
authors.initials: G
authors.lastname: Zhang
authors.forename: Hongzhong
authors.initials: H
authors.lastname: Wang
authors.forename: Maoxian
authors.initials: M
authors.lastname: He
authors.forename: Liping
authors.initials: L
authors.lastname: Xie
authors.forename: Rongqing
authors.initials: R
authors.lastname: Zhang
mesh_terms: D000595:Amino Acid Sequence; D060105:Animal Shells / Q000737:chemistry / Q000378:metabolism / Q000648:ultrastructure; D000818:Animals; D015153:Blotting, Western; D002119:Calcium Carbonate / Q000737:chemistry / Q000378:metabolism; D003460:Crystallization; D015870:Gene Expression / Q000187:drug effects; D046911:Macromolecular Substances / Q000378:metabolism*; D008855:Microscopy, Electron, Scanning; D008969:Molecular Sequence Data; D060734:Nacre / Q000737:chemistry / Q000378:metabolism*; D020319:Oligodeoxyribonucleotides, Antisense / Q000235:genetics / Q000494:pharmacology; D049911:Pinctada / Q000235:genetics / Q000378:metabolism*; D011506:Proteins / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D034622:RNA Interference; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid; D012694:Serine / Q000235:genetics / Q000378:metabolism
chemical_list: D046911:Macromolecular Substances; D060734:Nacre; D020319:Oligodeoxyribonucleotides, Antisense; D011506:Proteins; D012694:Serine; D002119:Calcium Carbonate