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P. Ahmann, K. Amyx, K.J. Lampi; Deamidation at the N–Terminal Domain Interface (Q70E), but Not the Homologue C–Terminal Domain Interface (Q162E) of Beta B2 Crystallin Altered the Protein Stability . Invest. Ophthalmol. Vis. Sci. 2005;46(13):3487.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose:Deamidation is the most prevalent post–translational modification in the aging lens and is increased in cataractous lenses. Each of the major crystallin polypeptides in the human lens is deamidated during aging, but the beta–crystallins are the most heavily deamidated. Our previous data showed that deamidation close to the highly conserved, hypothetical C–terminal intradomain–binding interface of beta B1 (Q204E) decreases the stability of the protein. The homologue amino acid sequence of beta B1 Q204 can be found in the N– and C–terminal domains of beta B2 (Q70 and Q162) and is close to the hypothetical interdomain–binding interface. Methods:The present study investigated the stability of Q70E and Q162E beta B2 during urea denaturation by tryptophan fluorescence measurement. Results:It was found that adding a negative charge in beta B2 close to the hypothetical C–terminal intradomain–binding interface does not alter the protein stability, but the N–terminal deamidation increases the stability of the protein. Interestingly the N–terminal deamidation of the beta B2 interface has the opposite effect compared to the C–terminal deamidation of the beta B1 interface, even though there are homologues interfaces. Conclusions:Deamidations close to the highly conserved (Q70E in beta B2) and (Q204E in beta B1) interfaces are able to alter the protein stability compared to the wild type. These stability alterations may be caused by (as yet unidentified) intramolecular structural changes. Such as reductions of hydrophobic pockets in the native state, which can lead to more (C–terminal) or less (N–terminal) forming of aggregations under unfolding conditions.
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