Involved in protein precursor import into chloroplasts. May be part of an intermediate translocation complex acting as a protein-conducting channel at the inner envelope. Seems to be specific for photosynthesis-related pre-proteins. Partially redundant with TIC20-IV, but not with TIC20-II or TIC20-V. Part of the Tic complex. Component of the 1-MD complex, composed of TIC20-I, TIC214, TIC100 and TIC56 (PubMed:23372012). Interacts with the translocating preproteins. Hydrolysis of ATP is essential for the formation of this complex(PubMed:19531596, PubMed:23372012). The 1-MD complex interacts with TIC21 (PubMed:19531596). Expressed in leaves, shoots and roots. High expression in mature photosynthetic tissues. Lower levels in non-photosynthetic tissues and roots. Highly expressed during germination and early development, with levels peaking at 25 days. Albino and seedling lethality. Tic20-I and tic20-IV double mutant is embryo lethal. Belongs to the Tic20 family.