A non-cytotoxic but ribonucleolytically specific ribotoxin variant: implication of tryptophan residues in the cytotoxicity of hirsutellin A
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Elías Herrero-Galán
Abstract
Ribotoxins are a family of toxic proteins that exert a highly specific cleavage at the universally conserved sarcin/ricin loop (SRL) of the larger rRNA molecule. Before this ribonucleolytic action, passage through the cell membrane is a necessary step for ribotoxin internalization and the limiting factor for cytotoxicity. Although extensive knowledge of their ribonucleolytic activity and substrate recognition has been accumulated, little is known about the mechanisms of cell entry of ribotoxins. Hirsutellin A (HtA) is a recently described member of this family, which accommodates the main abilities of previously characterized ribotoxins into a shorter sequence, but exhibits some differences regarding membrane interaction properties. This work investigates the contribution of tryptophan (Trp) residues 71 and 78 to both endoribonucleolytic activity and cellular toxicity of this ribotoxin. Substitution mutants W71F and W78F, as well as the double mutant W71/78F, were obtained and assayed against isolated ribosomes, synthetic SRL, and human tumor cells. The results provide evidence that cell membrane passage and internalization, as well as substrate-specific recognition, require the participation of the region involving both Trp 71 and Trp 78. Additionally, the mutant W71/78F is the first non-cytotoxic but specific ribosome-cleaving ribotoxin mutant obtained to date.
©2012 by Walter de Gruyter Berlin Boston
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- Masthead
Artikel in diesem Heft
- Review
- The critical role of adrenomedullin and its binding protein, AMBP-1, in neuroprotection
- Minireview
- Ubiquilins in the crosstalk among proteolytic pathways
- Protein Structure and Function
- A non-cytotoxic but ribonucleolytically specific ribotoxin variant: implication of tryptophan residues in the cytotoxicity of hirsutellin A
- The composite nature of the interaction between nuclear receptors EcR and DHR38
- Tmem27 dimerization, deglycosylation, plasma membrane depletion, and the extracellular Phe-Phe motif are negative regulators of cleavage by Bace2
- New ketomethylene inhibitor analogues: synthesis and assessment of structural determinants for N-domain selective inhibition of angiotensin-converting enzyme
- Cadherin-related protein 24 induces morphological changes and partial cell polarization by facilitating direct cell-cell interactions
- Molecular Medicine
- Analysis of tissue and salivary nicotinamide N-methyltransferase in oral squamous cell carcinoma: basis for the development of a noninvasive diagnostic test for early-stage disease
- Cell Biology and Signaling
- Mitochondrial protein import pathways are functionally conserved among eukaryotes despite compositional diversity of the import machineries
- Small molecule inhibitors of the c-Jun N-terminal kinase (JNK) possess antiviral activity against highly pathogenic avian and human pandemic influenza A viruses
- Matriptase-2 (TMPRSS6) is directly up-regulated by hypoxia inducible factor-1: identification of a hypoxia-responsive element in the TMPRSS6 promoter region
- Rab1 interacts directly with the β2-adrenergic receptor to regulate receptor anterograde trafficking
- Masthead
- Masthead
