Updated publication reference for PubMed record(s): 30865669. The protein import machinery is essential for chloroplast biogenesis, but knowledge on its exact functioning and the subunits involved in protein translocation is incomplete. Using TAP-tagged Toc159, we reproducibly identified a translocase interaction network that comprises in addition to known TOC members, the 1-MDa TIC complex, six FtsH/FtsHi proteases, Tic110, the KOC1 kinase and several other proteins, some of which with unknown function. The analysis of sub-complexes constituting the Toc159 interaction network in wildtype and a mutant defective in the 1-MDa TIC complex (tic56-3) revealed that the TOC and FtsH/FtsHi complex(es) accumulate independently of the TIC complex as do most other proteins in the network. An exception is a glycine-rich protein of 23 kDa that co-migrates with the 1-MDa complex and is co-regulated with its subunits in tic56-3. This protein was tentatively designated as Tic23. Tic23 abundance is significantly decreased in tic20-I mutant plants and the protein is completely absent from tic56-1 and Spectinomycin-treated wildtype plants lacking Tic214, suggesting a mutual dependency between its accumulation and intactness of the 1-MDa complex. Likewise, tic23-I mutants expressing reduced levels of Tic23 are pale-green and accumulate significantly decreased amounts of Tic20-I. Similar to tic56-3 plastids, the in vitro protein import capacity of tic23-I mutants is not affected. Taken together our results identify Tic23 as an additional component of the 1-MDa TIC complex that is required for complex stability and assembly while it serves complex-mediated functions other than protein import.