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Thu, 16 Nov 2017
Protein transport into peroxisomes: The peroxisomal targeting signal type-2 is recognized by a bipartite receptor complex

Time: 10.30 AM - 11.30 AM

Venue: Cysteine, Level 7 (30 Biopolis Street, Matrix)

Speaker: Dr. Markus Kunze, Senior Scientist, Department for Pathobiology of the Nervous System at the Center for Brain Research of the Medical University of Vienna


In eukaryotic cells the compartmentation of proteins into membrane bound compartments requires active transport processes. This transport depends on the interaction between a targeting signal encoded in the primary sequence of the protein and a receptor protein, which transfers its cargo to the import machinery of the organelle. Among all organelles peroxisomes have an exceptional state, because they import all matrix proteins in a folded state. Import of soluble proteins into peroxisomes can be mediated by one of two types of peroxisomal targeting signals residing either at the extreme C-terminus (PTS1) or close to the N-terminus (PTS2). Studying PTS2 motifs in a reporter protein based mammalian system we elucidated the structural properties of this type of targeting signal and characterized its interaction with its receptor protein PEX7. Furthermore, we demonstrate that the interaction between PEX7 and its co-receptor PEX5 is not only necessary to facilitate the transport of cargo loaded receptor to the peroxisomal membrane, but also stabilizes the interaction between PEX7 and its PTS2-carrying cargo proteins. This raised the question, whether the co-receptor poses additional restrictions on the properties of PTS2 motifs. Thus, we systematically compared functional PTS2 motifs with peptide sequences presenting as dysfunctional PTS2-like motifs. This widened the number of positions affecting the quality of PTS2 motifs and provided evidence for taxon-specific differences between animal and plant PTS2 motifs. Altogether, we provide evidence that the transport of PTS2-carrying proteins into peroxisomes is critically dependent on the formation of a trimeric complex consisting of the PTS2, the receptor PEX7 and the co-receptor PEX5.

About The Speaker
Markus studied Biochemistry and Biology/Botany at the University of Vienna. In recent years, he has contributed to and led a subproject in the EU-funded project "PEROXISOMES - Integrated project to decipher the biological function of peroxisomes in health and disease" and is now Senior Scientist in the Department for Pathobiology of the Nervous System at the Center for Brain Research of the Medical University of Vienna, Austria.

Dr. Sebastian Maurer-Stroh, Senior Principal Investigator / Programme Director Human Infectious Diseases

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