Characterization of AMBN I and II Isoforms and Study of Their Ca²⁺-Binding Properties

• Main Authors: Veronika Vetyskova, Monika Zouharova, Lucie Bednarova, Ondřej Vaněk, Petra Sázelová, Václav Kašička, Jiri Vymetal, Jaroslav Srp, Michaela Rumlová, Tatsiana Charnavets, Klara Postulkova, Janne E. Reseland, Kristyna Bousova, Jiri Vondrasek
• Format: Article
• Language: English
• Published: MDPI AG 2020-12-01
• Series: International Journal of Molecular Sciences
• Subjects: ameloblastin; biomineralization; oligomerization; calcium binding; intrinsically disordered protein (IDPs)
• Online Access: https://www.mdpi.com/1422-0067/21/23/9293
• ISSN: 1661-6596; 1422-0067

Ameloblastin (Ambn) as an intrinsically disordered protein (IDP) stands for an important role in the formation of enamel—the hardest biomineralized tissue commonly formed in vertebrates. The human ameloblastin (AMBN) is expressed in two isoforms: full-length isoform I (AMBN ISO I) and isoform II (AMBN ISO II), which is about 15 amino acid residues shorter than AMBN ISO I. The significant feature of AMBN—its oligomerization ability—is enabled due to a specific sequence encoded by exon 5 present at the N-terminal part in both known isoforms. In this study, we characterized AMBN ISO I and AMBN ISO II by biochemical and biophysical methods to determine their common features and differences. We confirmed that both AMBN ISO I and AMBN ISO II form oligomers in in vitro conditions. Due to an important role of AMBN in biomineralization, we further addressed the calcium (Ca²⁺)-binding properties of AMBN ISO I and ISO II. The binding properties of AMBN to Ca²⁺ may explain the role of AMBN in biomineralization and more generally in Ca²⁺ homeostasis processes.