Life Sciences BG | Specific amino acids in the BAR domain allow homodimerization and prevent heterodimerization of sorting nexin 33

English

Specific amino acids in the BAR domain allow homodimerization and prevent heterodimerization of sorting nexin 33

Sorting nexin 33 (SNX33) is a homolog of the endocytic protein SNX9 and has been implicated in actin polymerization and the endocytosis of the amyloid precursor protein. SNX33 belongs to the large family of BAR domain-containing proteins, which alter cellular protein trafficking by modulating cellular membranes and the cytoskeleton. Some BAR domains engage in homodimerization, whereas other BAR domains also mediate heterodimerization between different BAR domain-containing proteins. The molecular basis for this difference is not yet understood. Using coimmunoprecipitations we report that SNX33 forms homodimers, but not heterodimers with other BAR domain containing proteins, such as SNX9. Domain deletion analysis revealed that the BAR domain, but not the SH3 domain, was required for homodimerization of SNX33. Additionally, the BAR domain prevented the heterodimerization between SNX9 and SNX33, as determined by domain swap experiments. Molecular modelling of the SNX33 BAR domain structure revealed that key amino acids located at the BAR domain dimer interface of the SNX9 homodimer are not conserved in SNX33. Replacing these amino acids in SNX9 with the corresponding amino acids of SNX33 allowed the mutant SNX9 to heterodimerize with SNX33. Taken together, this study identifies critical amino acids within the BAR domains of SNX9 and SNX33 as determinants for the specificity of BAR domain-mediated interactions and suggests that SNX9 and SNX33 have distinct molecular functions.

Read the original article at BJ Cell.

Published: Nov 2010, Updated: 7th Nov

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