Tropomyosin induces the synthesis of magnesian calcite in sea urchin spines

Yugo Kato; Woosuk Ha; Zehua Zheng; Lumi Negishi; Jun Kawano; Yoshihisa Kurita; Hitoshi Kurumizaka; Michio Suzuki

doi:10.1016/j.jsb.2024.108074

Tropomyosin induces the synthesis of magnesian calcite in sea urchin spines

J Struct Biol. 2024 Mar 1;216(2):108074. doi: 10.1016/j.jsb.2024.108074. Online ahead of print.

Authors

Yugo Kato¹, Woosuk Ha¹, Zehua Zheng¹, Lumi Negishi², Jun Kawano³, Yoshihisa Kurita⁴, Hitoshi Kurumizaka², Michio Suzuki⁵

Affiliations

¹ Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, the University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan.
² Institute for Quantitative Biosciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan.
³ Department of Earth and Planetary Sciences, Faculty of Science, Hokkaido University, N10 W8, Kita-ku, Sapporo 060-0810, Japan.
⁴ Graduate School of Agricultural Science, Kyushu University, 4-46-24 Tsuyazaki, Fukutsu-shi, Fukuoka 811-3304, Japan.
⁵ Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, the University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan. Electronic address: amichio@g.ecc.u-tokyo.ac.jp.

PMID: 38432597
DOI: 10.1016/j.jsb.2024.108074

Abstract

Calcium carbonate is present in many biominerals, including in the exoskeletons of crustaceans and shells of mollusks. High Mg-containing calcium carbonate was synthesized by high temperatures, high pressures or high molecular organic matter. For example, biogenic high Mg-containing calcite is synthesized under strictly controlled Mg concentration at ambient temperature and pressure. The spines of sea urchins consist of calcite, which contain a high percentage of magnesium. In this study, we investigated the factors that increase the magnesium content in calcite from the spines of the sea urchin, Heliocidaris crassispina. X-ray diffraction and inductively coupled plasma mass spectrometry analyses showed that sea urchin spines contain about 4.8% Mg. The organic matrix extracted from the H. crassispina spines induced the crystallization of amorphous phase and synthesis of magnesium-containing calcite, while amorphous was synthesized without SUE (sea urchin extract). In addition, aragonite was synthesized by SUE treated with protease-K. HC tropomyosin was specifically incorporated into Mg precipitates. Recombinant HC-tropomyosin induced calcite contained 0.1-2.5% Mg synthesis. Western blotting of sea urchin spine extracts confirmed that HC tropomyosin was present in the purple sea urchin spines at a protein weight ratio of 1.5%. These results show that HC tropomyosin is one factor that increases the magnesium concentration in the calcite of H. crassispina spines.

Keywords: Biomineralization; Magnesian calcite; Sea urchin; Spine; Tropomyosin.