Coral acid rich protein selects vaterite polymorph in vitro

Laipnik, Ra'anan; Bissi, Veronica; Sun, Chang-Yu; Falini, Giuseppe; Gilbert, Pupa U. P. A.; Mass, Tali

doi:10.1016/j.jsb.2019.107431

Title: Coral acid rich protein selects vaterite polymorph in vitro

Journal Article · Sat Feb 01 00:00:00 EST 2020 · Journal of Structural Biology

DOI:https://doi.org/10.1016/j.jsb.2019.107431· OSTI ID:2325189

Laipnik, Ra'anan; Bissi, Veronica; Sun, Chang-Yu;

; Gilbert, Pupa U. P. A.;

Corals and other biomineralizing organisms use proteins and other molecules to form different crystalline polymorphs and biomineral structures. In corals, it’s been suggested that proteins such as Coral Acid Rich Proteins (CARPs) play a major role in the polymorph selection of their calcium carbonate (CaCO₃) aragonite exoskeleton. To date, four CARPs (1–4) have been characterized: each with a different amino acid composition and different temporal and spatial expression patterns during coral developmental stages. Interestingly, CARP3 is able to alter crystallization pathways in vitro, yet its function in this process remains enigmatic. To better understand the CARP3 function, we performed two independent in vitro CaCO3 polymorph selection experiments using purified recombinant CARP3 at different concentrations and at low or zero Mg²⁺ concentration. Our results show that, in the absence of Mg²⁺, CARP3 selects for the vaterite polymorph and inhibits calcite. However, in the presence of a low concentration of Mg²⁺ and CARP3 both Mg-calcite and vaterite are formed, with the relative amount of Mg-calcite increasing with CARP3 concentration. In all conditions, CARP3 did not select for the aragonite polymorph, which is the polymorph associated to CARP3 in vivo, even in the presence of Mg²⁺ (Mg:Ca molar ratio equal to 1). Our results further emphasize the importance of Mg:Ca molar ratios similar to that in seawater (Mg:Ca equal to 5) and the activity of the biological system in a aragonite polymorph selection in coral skeleton formation.

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Research Organization:: Univ. of Wisconsin, Madison, WI (United States); Univ. of California, Oakland, CA (United States)

Sponsoring Organization:: USDOE Office of Science (SC)

Grant/Contract Number:: FG02-07ER15899; AC02-05CH11231

OSTI ID:: 2325189

Alternate ID(s):: OSTI ID: 1800427

Journal Information:: Journal of Structural Biology, Journal Name: Journal of Structural Biology Vol. 209 Journal Issue: 2; ISSN 1047-8477

Publisher:: ElsevierCopyright Statement

Country of Publication:: United States

Language:: English

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