Protein localization

Stable Identifier
Homo sapiens
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Protein localization encompasses the processes that establish and maintain proteins at specific locations. Mechanisms that target proteins to particular locations in the cell typically involve a motif in the targeted protein that interacts with proteins located at the destination (reviewed in Bauer et al. 2015).
Mitochondrial proteins encoded in the nucleus may be targeted to the outer membrane, intermembrane space, inner membrane, or the matrix (reviewed in Kutik et al. 2007, Milenkovic et al. 2007, Bolender et al. 2008, Ender and Yamano 2009, Wiedemann and Pfanner 2017, Kang et al. 2018). A presequence or an internal targeting sequence causes a protein in the cytosol to interact with the TOMM40:TOMM70 complex in the outer mitochondrial membrane. After passage across the outer membrane, sequence motifs cause proteins to be targeted to the outer membrane via the SAMM50 complex, to the inner membrane via the TIMM22 or TIMM23 complexes, to the matrix via the TIMM23 complex, or proteins may fold and remain in the intermembrane space.
All of the proteins contained in the peroxisomal matrix are imported from the cytosol by a unique mechanism that does not require the imported proteins to be unfolded as they cross the membrane (reviewed in Ma et al. 2011, Fujiki et al. 2014, Francisco et al. 2017). In the cytosol, receptor proteins, PEX5 and PEX7, bind to specific sequence motifs in cargo proteins and then interact with a protein complex containing PEX13, PEX14, PEX2, PEX10, and PEX12 in the peroxisome membrane. The cargo proteins then pass through a proteinaceous channel in the membrane and PEX5 is recycled by a mechanism involving ubiquitination and deubiquitination.
Most peroxisomal membrane proteins (PMPs) are inserted into the peroxisomal membrane by the receptor-chaperone PEX19 and the docking receptor PEX3 (reviewed in Ma et al. 2011, Fujiki et al. 2014). PEX19 binds the PMP as it is translated in the cytosol. The PEX19:PMP complex then interacts with PEX3 located in the peroxisomal membrane. Through a mechanism that is not yet clear, the PMP is inserted into the peroxisomal membrane and PEX19 dissociates from PEX3.

Literature References
PubMed ID Title Journal Year
17696772 Diverse mechanisms and machineries for import of mitochondrial proteins

Pfanner, N, Milenkovic, D, Müller, J, Stojanovski, D, Chacinska, A

Biol Chem 2007
17998403 Cooperation of translocase complexes in mitochondrial protein import

Pfanner, N, Wiedemann, N, Meyer, HE, Guiard, B, Kutik, S

J Cell Biol 2007
19453276 Multiple pathways for mitochondrial protein traffic

Yamano, K, Endo, T

Biol Chem 2009
18174896 Multiple pathways for sorting mitochondrial precursor proteins

Pfanner, N, Wagner, R, Sickmann, A, Bolender, N, Meisinger, C

EMBO Rep 2008
28301740 Mitochondrial Machineries for Protein Import and Assembly

Wiedemann, N, Pfanner, N

Annu. Rev. Biochem. 2017
28765093 Mitochondrial protein transport in health and disease

Kang, Y, Stojanovski, D, Fielden, LF

Semin. Cell Dev. Biol. 2018
25177298 Peroxisome biogenesis in mammalian cells

Honsho, M, Mukai, S, Okumoto, K, Tamura, S, Fujiki, Y

Front Physiol 2014
28787099 Protein transport into peroxisomes: Knowns and unknowns

Barros-Barbosa, A, Rodrigues, TA, Dias, AF, Bicho, D, Azevedo, JE, Francisco, T

Bioessays 2017
26172624 Mechanisms Regulating Protein Localization

Corbett, AH, Doetsch, PW, Bauer, NC

Traffic 2015
21464226 Peroxisome assembly: matrix and membrane protein biogenesis

Subramani, S, Ma, C, Agrawal, G

J. Cell Biol. 2011
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