Involved in protein precursor import into chloroplasts. Partially redundant with TIC20-I, but not with TIC20-II or TIC20-V. Part of the Tic complex. Expressed in roots,seeds and non-photosynthetic tissues. Low levels in leaves. Expressed throughout development. No visible phenotype. Tic20-I and tic20-IV double mutant is embryo lethal. Belongs to the Tic20 family.