Involved in protein precursor import into chloroplasts. Forms a voltage-dependent cation-selective channel at the inner envelope of chloroplasts, which specifically responds to a transit peptide. Calcium acts as an effector of gating and selectivity. Part of the Tic complex. Interacts with TIC32, HSP93 and CPN60. Interacts with the Toc complex components TOC75 and TOC159. Binds specifically chloroplast pre-proteins. Down-regulated by cold stress. The N1 region (38-149) is sufficient for re-targeting to the inner membrane and proper insertion. The N2 region (150-269) may act as a start transfer signal, but it cannot direct proteins to the inner envelope. Contains at least one interchain redox-active disulfide bond. PubMed:9632730 shows that the region 121-996 is located in the stroma while PubMed:18986981 indicates that it contains probably 4 trans-membrane domains resulting in 2 regions in the intermembrane space localized to form supercomplexes with the TOC machinery and to receive the transit peptide of pre-proteins. Inserts into the inner envelope membrane from the stroma after import from the cytoplasm. Belongs to the chloroplast envelope anion channel-forming Tic110 (TC 1.A.18) family.