Heat-Triggered Conversion of Protofibrils into Mature Amyloid Fibrils of 2-Microglobulin
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- 作者：Kenji Sasahara ; Hisashi Yagi ; Hironobu Naiki ; Yuji Goto
- 刊名：Biochemistry
- 出版年：2007
- 出版时间：March 20, 2007
- 年：2007
- 卷：46
- 期：11
- 页码：3286 - 3293
- 全文大小：479K
- 年卷期：v.46,no.11(March 20, 2007)
- ISSN：1520-4995
文摘
Heat-triggered conversion of the salt-induced thin and flexible protofibrils into well-organizedthick and straight mature amyloid fibrils was achieved with 
2-microglobulin, a protein responsible fordialysis-related amyloidosis. First, protofibrils that formed spontaneously at pH 2.5 in the presence of 0.5M NaCl were aggregated by agitating the solution. Second, the aggregated protofibrils were heated in acell of a differential scanning calorimeter (DSC). The DSC thermogram showed an exothermic transitionwith sigmoidal temperature dependence, resulting in a remarkably large decrease in the heat capacity ofthe solution. Third, on the basis of electron microscopy together with circular dichroism spectroscopy,seeding experiments, and a thioflavin T binding assay, the sigmoidal transition was found to representthe conversion of protofibrils into mature amyloid fibrils. Furthermore, DSC thermograms obtained atvarious heating rates revealed that the transition curve depends on the heating rate, implying that theeffects of heat associated with the conversion to the mature fibrils are kinetically controlled, precludingan interpretation in terms of equilibrium thermodynamics. Taken together, these results highlight theimportance of the change in heat capacity in addressing the biological significance of interactions betweensolvent water and amyloid fibrils and, moreover, in detecting the formation of amyloid fibrils.
2-microglobulin, a protein responsible fordialysis-related amyloidosis. First, protofibrils that formed spontaneously at pH 2.5 in the presence of 0.5M NaCl were aggregated by agitating the solution. Second, the aggregated protofibrils were heated in acell of a differential scanning calorimeter (DSC). The DSC thermogram showed an exothermic transitionwith sigmoidal temperature dependence, resulting in a remarkably large decrease in the heat capacity ofthe solution. Third, on the basis of electron microscopy together with circular dichroism spectroscopy,seeding experiments, and a thioflavin T binding assay, the sigmoidal transition was found to representthe conversion of protofibrils into mature amyloid fibrils. Furthermore, DSC thermograms obtained atvarious heating rates revealed that the transition curve depends on the heating rate, implying that theeffects of heat associated with the conversion to the mature fibrils are kinetically controlled, precludingan interpretation in terms of equilibrium thermodynamics. Taken together, these results highlight theimportance of the change in heat capacity in addressing the biological significance of interactions betweensolvent water and amyloid fibrils and, moreover, in detecting the formation of amyloid fibrils.