Peroxisomal membrane proteins contain common Pex19p-binding sites that are an integral part of their targeting signals

• Published in: Molecular biology of the cell 2004-07, Vol.15 (7), p.3406-3417
• Main Authors: Rottensteiner, Hanspeter, Kramer, Achim, Lorenzen, Stephan, Stein, Katharina, Landgraf, Christiane, Volkmer-Engert, Rudolf, Erdmann, Ralf
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Binding Sites - genetics; Membrane Proteins - analysis; Membrane Proteins - genetics; Membrane Proteins - metabolism; Molecular Sequence Data; Peroxisomes - chemistry; Peroxisomes - metabolism; Protein Sorting Signals; Saccharomyces cerevisiae; Saccharomyces cerevisiae - metabolism; Saccharomyces cerevisiae Proteins - analysis; Saccharomyces cerevisiae Proteins - genetics; Saccharomyces cerevisiae Proteins - metabolism; Two-Hybrid System Techniques
• ISSN: 1059-1524; 1939-4586
• DOI: 10.1091/mbc.E04-03-0188

Targeting of peroxisomal membrane proteins (PMPs) is a multistep process that requires not only recognition of PMPs in the cytosol but also their insertion into the peroxisomal membrane. As a consequence, targeting signals of PMPs (mPTS) are rather complex. A candidate protein for the PMP recognition event is Pex19p, which interacts with most PMPs. However, the respective Pex19p-binding sites are ill-defined and it is currently disputed whether these sites are contained within mPTS. By using synthetic peptide scans and yeast two-hybrid analyses, we determined and characterized Pex19p-binding sites in Pex11p and Pex13p, two PMPs from Saccharomyces cerevisiae. The sites turned out to be composed of a short helical motif with a minimal length of 11 amino acids. With the acquired data, it proved possible to predict and experimentally verify Pex19p-binding sites in several other PMPs by applying a pattern search and a prediction matrix. A peroxisomally targeted Pex13p fragment became mislocalized to the endoplasmic reticulum in the absence of its Pex19p-binding site. By adding the heterologous binding site of Pex11p, peroxisomal targeting of the Pex13p fragment was restored. We conclude that Pex19p-binding sites are well-defined entities that represent an essential part of the mPTS.