Involved in protein precursor import into chloroplasts. Part of the redox regulon consisting of TIC32, TIC 55 and TIC62. Has a NADPH-dependent dehydrogenase activity, but only after preincubation with lipids. Part of the Tic complex. Interacts with TIC110 (via N-terminus) and with calmodulin in a calcium-dependent manner. Interacts with TIC22 during import into chloroplast. The N-terminus (1-10) forms an essential portion of the targeting information. NADPH and calmodulin binding is mutually exclusive. Dissociates from TIC110 after addition of NADPH. Imported into the chloroplast in the absence of a cleavable N-terminal pre-sequence. Not imported via the Toc complex. Belongs to the short-chain dehydrogenases/reductases (SDR) family.