Voltage-dependent high-conductance channel with a slight cation-selectivity; selective for amino acids but excludes triosephosphates or uncharged sugars (By similarity). Non-essential amino acid-selective channel protein and translocation pore for NADPH:protochlorophyllide oxidoreductase A (PORA) and possibly PORB. Involved in PORA precursor (pPORA) import and thus confers photoprotection onto etiolated seedlings during greening. Stimulated by GTP. Homodimer and oligomers in membrane (By similarity). Forms large complexes including TOC33, pPORA and OEP161 during pPORA import into plastids at the plastid envelope membrane. Expressed predominantly in leaves and cotyledons. Transient reduction upon de-etiolation (illuminated 5-day-old etiolated seedlings) (at protein level). Strongly induced by low-temperature stress and weakly in response to osmotic stress, salicylic acid (SA) and exogenous abscisic acid (ABA) treatments. Strong red Pchlide fluorescence after 3.5-4 days of growth in the dark, and cell death after subsequent illumination. Conditional seedling lethal phenotype related to defects in import and assembly of NADPH:protochlorophyllide (Pchlide) oxidoreductase A; excess Pchlide accumulated in the dark operates as photosensitizer and provokes cell death during greening. Belongs to the Tim17/Tim22/Tim23 family. Plastid outer envelope porin OEP16 (TC 1.B.30) subfamily.