Ciccotosto GD, Tew D, Curtain CC, Smith D, Carrington D, Masters CL, Bush AI, Cherny RA, Cappai R, Barnham KJ. Enhanced toxicity and cellular binding of a modified amyloid beta peptide with a methionine to valine substitution. J Biol Chem. 2004 Oct 8;279(41):42528-34. PubMed.
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Leeds Trinity University
This paper has some interesting results and some elegant experimentation.
However, I would like to propose an alternative interpretation of the results obtained for inhibition of amyloid-β toxicity by catalase.
Zhang et al. have demonstrated that catalase inhibition of amyloid-β toxicity is independent of H2O2 generation, and I identified a binding interaction between catalase and amyloid-β (Milton, 1999).
The key amyloid-β residues for this interaction are 31-35. The substitution of Met 35 for Val in this paper may therefore significantly alter the binding affinity of catalase for amyloid-β and would provide an alternative explanation for the failure of catalase to totally protect against the toxicity of this mutated amyloid-β form.
The catalase amyloid-β binding domain has been identified (Milton et al., 2001) and would provide a ready tool to assess whether the protection required an H2O2 degrading activity or was due to the binding of amyloid-β to catalase.
References:
Zhang Z, Rydel RE, Drzewiecki GJ, Fuson K, Wright S, Wogulis M, Audia JE, May PC, Hyslop PA. Amyloid beta-mediated oxidative and metabolic stress in rat cortical neurons: no direct evidence for a role for H2O2 generation. J Neurochem. 1996 Oct;67(4):1595-606. PubMed.
Milton NG. Amyloid-beta binds catalase with high affinity and inhibits hydrogen peroxide breakdown. Biochem J. 1999 Dec 1;344 Pt 2:293-6. PubMed.
Milton NG, Mayor NP, Rawlinson J. Identification of amyloid-beta binding sites using an antisense peptide approach. Neuroreport. 2001 Aug 8;12(11):2561-6. PubMed.
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