The biological activity of Humanin analogs correlates with structure stabilities in solution |
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Authors: | Arakawa Tsutomu Niikura Takako Kita Yoshiko |
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Affiliation: | a Alliance Protein Laboratories, 3957 Corte Cancion, Thousand Oaks, CA 91360, United States b Faculty of Health Sciences, Simon Fraser University, Burnaby, BC, V5A 1S6, Canada c Department of Pharmacology, KEIO University School of Medicine, Tokyo 160-8582, Japan |
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Abstract: | A single mutation has resulted in large differences in neuroprotective activity of a 24 amino acid Humanin (HN). A mutation of Ser7Ala (S7A-HN) resulted in loss of activity, while a mutation of Ser14Gly (S14G-HN) resulted in about 1000-fold increase. The mechanism of the effects conferred by these mutations have been totally unclear, although our recent structure analysis suggested a possibility of the effect of mutation on the structure stability. Here, we have studied the effects of buffer and temperature on the structure of these three HN peptides. These peptides showed a similar disordered structure at 10 °C in 10 mM phosphate, pH 6.0. They were also similar in phosphate-buffered saline (PBS) as long as the temperature was kept low at 10 °C. However, a large difference was observed in both phosphate buffer and PBS between the peptides, when the temperature was raised to a physiological temperature of 37 °C. While S14G-HN showed small changes in both solutions at 37 °C, the less active HN and inactive S7A-HN showed much larger changes under the identical conditions. In addition, it appeared that structure change at 37 °C was faster for S7A-HN than HN. These results show that the structure stability at 37 °C increases in the order of S7A-HN, HN and S14G-HN, in correlation with their neuroprotective activities. |
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Keywords: | Humanin Structure stability Circular dichroism Analog β-Sheet structure |
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