Hossain Tofazzal, Teshiba Satoshi, Shigeoka Yuichi, Fujisawa Tetsuro, Inoko Yoji, Sakano Daisuke, Yamamoto Kohji, Banno Yutaka, Aso Yoichi
Institute of Genetic Resources, Faculty of Agriculture, Kyushu University, Fukuoka, Japan.
Biosci Biotechnol Biochem. 2010;74(8):1556-63. doi: 10.1271/bbb.100131. Epub 2010 Aug 7.
sHSP20.8 and sHSP19.9 are silkworm small-heat shock proteins (sHSPs) comprising a number of polypeptides of molecular sizes of several tens of kilodaltons as subunits. The structural properties of sHSPs were investigated. sHSP19.9 was found to be aggregated by itself during incubation at 60 degrees C. Aggregation was suppressed in the presence of dithiothreitol and at high ionic strength. In contrast, sHSP20.8 was not aggregated. Aggregation of sHSP19.9 was partially suppressed by sHSP20.8 and in the presence of catalase as a target protein. Based on changes in small-angle X-ray scattering, it is possible that the molecular size of sHSP19.9 is larger than that of sHSP20.8, and that their molecular sizes increase with increasing temperature in a reversible, biphasic manner. sHSPs did not protect catalase from thermal inactivation, but protected it from precipitation by forming a soluble complex. sHSP20.8 and sHSP19.9 with dithiothreitol were stable against lyophilization, autoclaving at 120 degrees C, and boiling.
小分子热激蛋白20.8（sHSP20.8）和小分子热激蛋白19.9（sHSP19.9）是家蚕小分子热激蛋白（sHSPs），由若干分子大小为几十千道尔顿的多肽作为亚基组成。对sHSPs的结构特性进行了研究。发现sHSP19.9在60℃孵育时会自行聚集。在二硫苏糖醇存在和高离子强度下，聚集受到抑制。相比之下，sHSP20.8不会聚集。sHSP20.8以及作为靶蛋白的过氧化氢酶存在时，sHSP19.9的聚集会受到部分抑制。基于小角X射线散射的变化，sHSP19.9的分子大小可能大于sHSP20.8，并且它们的分子大小会随着温度升高以可逆的双相方式增加。sHSPs不能保护过氧化氢酶免受热失活，但通过形成可溶性复合物保护其免予沉淀。含有二硫苏糖醇的sHSP20.8和sHSP19.9对冻干、120℃高压灭菌和煮沸具有稳定性。
