Crystal structure of the trimeric N‐terminal domain of ciliate Euplotes octocarinatus centrin binding with calcium ions

Abstract

Centrin is a member of the EF-hand superfamily of calcium-binding proteins, a highly conserved eukaryotic protein that binds to Ca . Its self-assembly plays a causative role in the fiber contraction that is associated with the cell division cycle and ciliogenesis. In this study, the crystal structure of N-terminal domain of ciliate Euplotes octocarinatus centrin (N-EoCen) was determined by using the selenomethionine single-wavelength anomalous dispersion method. The protein molecules formed homotrimers. Every protomer had two putative Ca ion-binding sites I and II, protomer A, and C bound one Ca ion, while protomer B bound two Ca ions. A novel binding site III was observed and the Ca ion was located at the center of the homotrimer. Several hydrogen bonds, electrostatic, and hydrophobic interactions between the protomers contributed to the formation of the oligomer. Structural studies provided insight into the foundation for centrin aggregation and the roles of calcium ions.

The interplay of self-assembly and target binding in centrin 1 from Toxoplasma gondii

“…The understanding of the self-assembly properties of centrins in vitro has been a relevant topic for several years and many studies have demonstrated that these proteins are key structural components of Ca 2+ -sensitive filaments [ 17 , 19 , 44 , 45 ]. We found that TgCEN1 can self-assemble in the presence of Ca 2+ and that the assembly process depends on different physical and chemical factors, comprising Ca 2+ and protein concentration, temperature, ionic strength, and molecular hydrophobicity.…”

“…However, we cannot exclude an association model in which the N-terminal domains mediate the interaction between different monomers. Recently, the crystal structure of the trimeric N-terminal domain of Euplotes octocarinatus centrin was reported, underpinning the ability of the protein to self-associate in a mode of N-to-N [ 45 ]. Indeed, most of the crucial residues that contribute to the forming the homotrimer in EoCen are conserved also in TgCEN1 (Supplementary Figure S6).…”

Differential requirements for the EF-hand domains of human centrin 2 in primary ciliogenesis and nucleotide excision repair

“…Previous analyses have demonstrated that centrin forms large aggregates with both itself and its interactors, such as XPC (Araki et al, 2001), Kar1p (Spang et al, 1995), Sfi1p (Kilmartin, 2003) and CP110 (Tsang et al, 2006). Several studies have demonstrated the importance of calcium binding in self-aggregation of centrins from multiple species (Wiech et al, 1996;Tourbez et al, 2004;Yang et al, 2006;Li et al, 2006;Wang et al, 2018), as well as in the assembly of multimeric complexes with Sfi1p (Kilmartin, 2003;Li et al, 2006;Martinez-Sanz et al, 2006). Our data clearly indicate the need for calcium binding capacity in allowing the assembly of human centrin 2-SFI1-POC5 complexes, consistent with previous observations we made on the requirement for centrin in the assembly of POC5 aggregate structures (Dantas et al, 2013).…”