This entry represents the PEX5-related proteins (PEX5L, also known as TRIP8b) from vertebrates. It acts as an accessory subunit of hyperpolarization-activated cyclic nucleotide-gated (HCN) channels, regulating their cell-surface expression and cyclic nucleotide dependence [, ]. Interestingly, although PEX5L and PEX5 have structurally similar binding at their TPR domains, they bind to different substrates in vivo [].
Peroxisomal proteins catalyse metabolic reactions. The import of proteins from the cytosol into the peroxisomes matrix depends on more than a dozen peroxin (PEX) proteins, among which PEX5 and PEX7 serve as receptors that shuttle proteins bearing one of two peroxisome-targeting signals (PTSs) into the organelle. PEX5 is the PTS1 receptor, while PEX7 is the PTS2 receptor. In plants, PEX7 depends on PEX5 binding to deliver PTS2 cargo into the peroxisome, and PEX7 also facilitates PEX5 accumulation and import of PTS1 cargo into peroxisomes [, ]. This entry include PEX5 (also known as PTS1R) from animals, fungi and plants. This entry also includes PEX5L from vertebrates. PEX5 binds to the C-terminal PTS1-type tripeptide peroxisomal targeting signal (SKL-type) and plays an essential role in peroxisomal protein import [, , ]. Based on subcellular localization and binding properties mammalian PEX5 may function as a regulator in an early step of the PTS1 protein import process []. PEX5L acts as an accessory subunit of hyperpolarization-activated cyclic nucleotide-gated (HCN) channels, regulating their cell-surface expression and cyclic nucleotide dependence [, ]. Interestingly, although PEX5 and PEX5L have structurally similar binding at their TPR domains, they bind to different substrates in vivo [].
