The peroxisomal membrane protein Pex13p shows a novel mode of SH3 interaction |
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Authors: | Barnett P Bottger G Klein A T Tabak H F Distel B |
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Institution: | Department of Biochemistry, Academic Medical Center, University of Amsterdam, Meibergdreef 15, 1105 AZ Amsterdam, The Netherlands. |
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Abstract: | Src homology 3 (SH3) domains are small non-catalytic protein modules capable of mediating protein-protein interactions by binding to proline-X-X-proline (P-X-X-P) motifs. Here we demonstrate that the SH3 domain of the integral peroxisomal membrane protein Pex13p is able to bind two proteins, one of which, Pex5p, represents a novel non-P-X-X-P ligand. Using alanine scanning, two-hybrid and in vitro interaction analysis, we show that an alpha-helical element in Pex5p is necessary and sufficient for SH3 interaction. Sup pressor analysis using Pex5p mutants located in this alpha-helical element allowed the identification of a unique site of interaction for Pex5p on the Pex13p-SH3 domain that is distinct from the classical P-X-X-P binding pocket. On the basis of a structural model of the Pex13p-SH3 domain we show that this interaction probably takes place between the RT- and distal loops. Thus, the Pex13p-SH3-Pex5p interaction establishes a novel mode of SH3 interaction. |
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