a single peroxisomal targeting signal mediates matrix protein import in diatoms单一酶针对信号介导基质蛋白导入硅藻.pdfVIP

A Single Peroxisomal Targeting Signal Mediates Matrix Protein Import in Diatoms 1 1 1 2 1,2 Nicola H. Gonzalez , Gregor Felsner , Frederic D. Schramm , Andreas Klingl , Uwe-G. Maier , Kathrin Bolte1* ¨ 1 Laboratory for Cell Biology, Philipps University of Marburg, Marburg, Germany, 2 LOEWE-Zentrum fur Synthetische Mikrobiologie (SynMikro), Marburg, Germany Abstract Peroxisomes are single membrane bound compartments. They are thought to be present in almost all eukaryotic cells, although the bulk of our knowledge about peroxisomes has been generated from only a handful of model organisms. Peroxisomal matrix proteins are synthesized cytosolically and posttranslationally imported into the peroxisomal matrix. The import is generally thought to be mediated by two different targeting signals. These are respectively recognized by the two import receptor proteins Pex5 and Pex7, which facilitate transport across the peroxisomal membrane. Here, we show the first in vivo localization studies of peroxisomes in a representative organism of the ecologically relevant group of diatoms using fluorescence and transmission electron microscopy. By expression of various homologous and heterologous fusion proteins we demonstrate that targeting of Phaeodactylum tricornutum peroxisomal matrix proteins is mediated only by PTS1 targeting signals, also for proteins that are in other systems imported via a PTS2 mode of action. Additional in silico analyses suggest this surprising finding may also apply to further diatoms. Our data suggest that loss