9VSJ
Crystal structure of the genetically-encoded green calcium sensor icBTnC2 in its calcium bound-state
Summary for 9VSJ
| Entry DOI | 10.2210/pdb9vsj/pdb |
| Descriptor | icBTnC2 - the genetically-encoded green calcium sensor based on the fluorescent protein mBaoJin and calcium binding domain of C-terminal minimal domain of troponin C from Calypte Anna, DI(HYDROXYETHYL)ETHER, CALCIUM ION, ... (5 entities in total) |
| Functional Keywords | mbaojin2, green fluorescent protein, fluorescent protein, indicator, sensor, calcium |
| Biological source | synthetic construct |
| Total number of polymer chains | 1 |
| Total formula weight | 35320.05 |
| Authors | Boyko, K.M.,Nikolaeva, A.Y.,Dorovatovskii, P.V.,Vlaskina, A.V.,Agapova, Y.K.,Petrenko, D.E.,Subach, O.M.,Chelykhova, S.A.,Popov, V.O.,Subach, F.V. (deposition date: 2025-07-08, release date: 2025-09-17, Last modification date: 2026-09-30) |
| Primary citation | Chelykhova, S.A.,Subach, O.M.,Vlaskina, A.V.,Lesnov, G.D.,Romantsova, A.N.,Agapova, Y.K.,Petrenko, D.E.,Dorovatovskii, P.V.,Nikolaeva, A.Y.,Boyko, K.M.,Popov, V.O.,Zhou, S.,Piatkevich, K.D.,Subach, F.V. icBTnC2, a new green calcium indicator based on troponin C and mBaoJin, with enhanced photostability. Protein Sci., 35:e70499-e70499, 2026 Cited by PubMed Abstract: Genetically encoded green calcium indicators (GECIs) are broadly used for visualizing calcium transients in living cells. Among the diverse family of green GECIs, the Troponin C-based family offers potential advantages, including reduced calcium buffering, smaller molecular size, linear calcium response, and low cytotoxicity. However, the Troponin C-based GECIs with inverted calcium response are less developed compared to other popular GECIs, including GCaMPs and GECOs, and, as a consequence, have several drawbacks related to low dynamic range, brightness, photostability, and calcium ion sensitivity. To address these limitations, we developed a novel GECI, called icBTnC2, which incorporates Troponin C as a sensing moiety and the new bright photostable green FP mBaoJin as a reporting moiety. icBTnC2 demonstrated an inverted fluorescent response to calcium ion binding with a K of 62 nM. In terms of fluorescence contrast and calcium ion affinity in vitro, icBTnC2 was comparable to the best widely used calmodulin-based GECIs from the GCaMP family. icBTnC2 demonstrated superior photostability under wide-field fluorescence microscopy exhibiting 5.5-, 4.8-, 3.2-, 2.9-, and 1.3-fold higher photobleaching half-time compared to iYTnC2, mEGFP, NCaMP7, jGCaMP8f, and mBaoJin, respectively. The icBTnC2 indicator was benchmarked against other GECIs, such as jGCaMP8f, NCaMP7, iYTnC2, and R-GECO1, for visualization of calcium transients in mammalian cells and primary neuron cultures, and tested for calcium-dependent changes in fluorescence lifetime. Finally, we solved the crystal structure of the icBTnC2 indicator at 1.55 Å resolution in the calcium-bound state and, using directed mutagenesis, proposed the molecular basis of its fluorescent response to calcium ion binding. PubMed: 41685985DOI: 10.1002/pro.70499 PDB entries with the same primary citation |
| Experimental method | X-RAY DIFFRACTION (1.55 Å) |
Structure validation
Download full validation report
