Dataset Information

Substrate filtering by the active site crossover loop in UCHL3 revealed by sortagging and gain-of-function mutations.

ABSTRACT: Determining how deubiquitinating enzymes discriminate between ubiquitin-conjugated substrates is critical to understand their function. Through application of a novel protein cleavage and tagging technique, sortagging, we show that human UCHL3 and the Plasmodium falciparum homologue, members of the ubiquitin C-terminal hydrolase family, use a unique active site crossover loop to restrict access of bulky ubiquitin adducts to the active site. Although it provides connectivity for critical active site residues in UCHL3, physical integrity of the crossover loop is dispensable for catalysis. By enlarging the active site crossover loop, we have constructed gain-of-function mutants that can accept substrates that the parent enzyme cannot, including ubiquitin chains of various linkages.

SUBMITTER: Popp MW

PROVIDER: S-EPMC2635039 | biostudies-literature | 2009 Feb

REPOSITORIES: biostudies-literature

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Substrate filtering by the active site crossover loop in UCHL3 revealed by sortagging and gain-of-function mutations.

Popp Maximilian W MW Artavanis-Tsakonas Katerina K Ploegh Hidde L HL

The Journal of biological chemistry 20081201 6

Determining how deubiquitinating enzymes discriminate between ubiquitin-conjugated substrates is critical to understand their function. Through application of a novel protein cleavage and tagging technique, sortagging, we show that human UCHL3 and the Plasmodium falciparum homologue, members of the ubiquitin C-terminal hydrolase family, use a unique active site crossover loop to restrict access of bulky ubiquitin adducts to the active site. Although it provides connectivity for critical active s ...[more]

PMID: 19047059

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Project description:PTEN prevents tumor genesis by antagonizing the PI3 kinase/Akt pathway through D3 site phosphatase activity toward PI(3,4)P2 and PI(3,4,5)P3. The structural determinants of this important specificity remain unknown. Interestingly, PTEN shares remarkable homology to voltage-sensitive phosphatases (VSPs) that dephosphorylate D5 and D3 sites of PI(4,5)P2, PI(3,4)P2, and PI(3,4,5)P3. Since the catalytic center of PTEN and VSPs differ markedly only in TI/gating loop and active site motif, we wondered whether these differences explained the variation of their substrate specificity. Therefore, we introduced mutations into PTEN to mimic corresponding sequences of VSPs and studied phosphatase activity in living cells utilizing engineered, voltage switchable PTENCiV, a Ci-VSP/PTEN chimera that retains D3 site activity of the native enzyme. Substrate specificity of this enzyme was analyzed with whole-cell patch clamp in combination with total internal reflection fluorescence microscopy and genetically encoded phosphoinositide sensors. In PTENCiV, mutating TI167/168 in the TI loop into the corresponding ET pair of VSPs induced VSP-like D5 phosphatase activity toward PI(3,4,5)P3, but not toward PI(4,5)P2. Combining TI/ET mutations with an A126G exchange in the active site removed major sequence variations between PTEN and VSPs and resulted in D5 activity toward PI(4,5)P2 and PI(3,4,5)P3 of PTENCiV. This PTEN mutant thus fully reproduced the substrate specificity of native VSPs. Importantly, the same combination of mutations also induced D5 activity toward PI(3,4,5)P3 in native PTEN demonstrating that the same residues determine the substrate specificity of the tumor suppressor in living cells. Reciprocal mutations in VSPs did not alter their substrate specificity, but reduced phosphatase activity. In summary, A126 in the active site and TI167/168 in the TI loop are essential determinants of PTEN's substrate specificity, whereas additional features might contribute to the enzymatic activity of VSPs.

Dataset Information

Substrate filtering by the active site crossover loop in UCHL3 revealed by sortagging and gain-of-function mutations.

Publications

Substrate filtering by the active site crossover loop in UCHL3 revealed by sortagging and gain-of-function mutations.

Similar Datasets

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