title: N40, a novel nonacidic matrix protein from pearl oyster nacre, facilitates nucleation of aragonite in vitro.
abstract: A novel nonacidic matrix protein from pearl oyster nacre has been purified by cation-exchange chromatography. It was designated N40 for the nacreous protein of approximately 40 kDa. On the basis of the extraction method (with Tris-buffered Milli-Q water) and amino acid compositions (Gly- and Ala-rich), N40 was inferred to be a conventional "insoluble matrix protein". Crystallization experiments showed that N40 could facilitate the nucleation of aragonite drastically. So far, among the macromolecules that have been purified from the shell, N40 is an exclusive protein that can nucleate aragonite by itself, without the need for adsorption to a substrate. Thus, the present study has proposed the possibility that the nonacidic shell protein (maybe a conventional "insoluble framework protein") can also directly participate in aragonite nucleation and even act as a nucleation site. It is a valuable supplement to the classic biomineralization theory, in which the soluble acidic proteins of the shell are generally believed to function as a nucleation site.
authors.affiliation: Institute of Marine Biotechnology, Department of Biological Sciences and Biotechnology, and Protein Science Laboratory of the Ministry of Education, Tsinghua University, Beijing, China.
authors.forename: Zhenguang
authors.initials: Z
authors.lastname: Yan
authors.forename: Gu
authors.initials: G
authors.lastname: Jing
authors.forename: Ningping
authors.initials: N
authors.lastname: Gong
authors.forename: Changzhong
authors.initials: C
authors.lastname: Li
authors.forename: Yujuan
authors.initials: Y
authors.lastname: Zhou
authors.forename: Liping
authors.initials: L
authors.lastname: Xie
authors.forename: Rongqing
authors.initials: R
authors.lastname: Zhang
mesh_terms: D000143:Acids / Q000737:chemistry; D000596:Amino Acids / Q000378:metabolism; D000818:Animals; D002119:Calcium Carbonate / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D008855:Microscopy, Electron, Scanning; D049911:Pinctada / Q000737:chemistry / Q000378:metabolism*; D011506:Proteins / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism* / Q000648:ultrastructure; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D017550:Spectroscopy, Fourier Transform Infrared; D013059:Spectrum Analysis, Raman
chemical_list: D000143:Acids; D000596:Amino Acids; D011506:Proteins; D002119:Calcium Carbonate