In plants, 95% of proteins are nuclear encoded. Chloroplasts contain about 3000 proteins, of which thylakoid alone contain 100-150; 100 proteins of which 50% are plastid-encoded, and 150 proteins nuclear-encoded are localized to the lumen (Leister 2003, New et al. 2018). Furthermore, the photosynthetic electron transport chain within the thylakoid membrane, comprised of photosystem 2 (PS2), PS1, the B6F complex, and the ATP-synthase account for 75-100 of these proteins (Peltier et al. 2000). The remainder of proteins in thylakoid are involved in biogenesis as well as the regulation of the major photosynthetic complex (Kieselbach et al. 1998). Similarly, just about 99% of mitochondrial proteins are nuclear-encoded and synthesized as precursor proteins. Mitochondria, analogous to the chloroplast in plants, carry out multiple metabolic processes i.e. source of cellular ATP, amino acid metabolism, etc (Fukasawa et al. 2017). Currently, it has been found that mitochondria, in yeast and mammals alike, contain just about 1000-1500 proteins altogether, making these highly proteinaceous multicompartment plastids (Schmidt et al. 2010). Due to their energy-producing capabilities, protein sorting within and across the membrane is necessary. As previously mentioned, most of these proteins needed to create the photosynthetic electron transport machinery (or electron transport chain in mitochondria) both Eukaryotic and Prokaryotic systems have developed efficient ways to transport these proteins across plastid membranes. Signal transport sequence mediated transport and protein translocase sensing machinery can carry out the transport process, in a sophisticated and energy-efficient manner (Chaddock et al. 1995). In both bacteria and chloroplast, different translocation pathways have been well investigated and characterized. The most pronounced of them range from the translocase of the mitochondrial outer/inner membrane TOM/TIM, the translocase of the chloroplast outer and inner envelope (TOC/TIC), bacterial Sec, chloroplast Sec (cpSec), and the novel Tat pathway. All of these translocons have unique features to name a few; transport of nuclear-encoded proteins containing signal peptides, have multi-subunit/multi-spanning core proteins, and carry out precursor translocation in a nucleotide hydrolysis dependent manner and/or the presence of a proton motive force (PMF)(Schulz et al. 2015, Wasilewski et al. 2017). The TAT pathway has been of great interest due to its ability to translocate fully folded proteins and because of its sole energetic requirement being the PMF. We will describe the mechanistic aspect of the precursor translocation systems followed by a more detailed current knowledge of the TAT pathway mechanism and future endeavors.