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2010-09-20 01:54 |
据“每日科学”网站报道，科学家近日在号称世上最顽强细菌的体内中发现了他们一直找寻的化学抗氧化剂。研究结果刊登在9月3日的《公共科学图书馆—综合》（PLoS One）上。
(图片来源：Uniformed Services University of the Health Sciences)
相关仪器：Centriplus YM-3离心过滤器 SpeedVac离心浓缩仪 4100ZL型原子吸收光谱仪 高效液相色谱仪
完成人：迈克尔 戴利课题组/罗德尼 莱文课题组
实验室：美国军队卫生服务大学病理学系、三军放射生物学研究所 美国国立卫生研究院心肺血液研究所生物化学实验室
这种被称为“耐辐射奇球菌（Deinococcus radiodurans）”的细菌发现于上世纪50年代，其生命力异常顽强，就算是暴露在伽马射线、紫外线、干燥环境或者其他通过产生活性氧来杀死细胞的试剂当中，它依然能够存活。
在这项最新的研究中，科学家在这种球菌的细胞提取液中检测到含有二价锰的一些复合物，这些复合物可对纯蛋白、大肠杆菌以及人体细胞起到保护作用，使其免受电离辐射的伤害。在受到伽马射线的照射时，耐辐射奇球菌似乎会保存蛋白和DNA的分解物，并与二价锰结合，将缩氨酸和正磷酸盐进行混合，为强效活性氧清除系统提供原料。
可以预料的是，耐辐射奇球菌这种新型高效的化学保护机制，将为科学家研究如何应对各种环境下的氧化应激提供新思路
1 Department of Pathology, Uniformed Services University of the Health Sciences, Bethesda, Maryland, United States of America, 2 Armed Forces Radiobiology Research Institute, Uniformed Services University of the Health Sciences, Bethesda, Maryland, United States of America, 3 Laboratory of Biochemistry, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland, United States of America
For Deinococcus radiodurans and other bacteria which are extremely resistant to ionizing radiation, ultraviolet radiation, and desiccation, a mechanistic link exists between resistance, manganese accumulation, and protein protection. We show that ultrafiltered, protein-free preparations of D. radiodurans cell extracts prevent protein oxidation at massive doses of ionizing radiation. In contrast, ultrafiltrates from ionizing radiation-sensitive bacteria were not protective. The D. radiodurans ultrafiltrate was enriched in Mn, phosphate, nucleosides and bases, and peptides. When reconstituted in vitro at concentrations approximating those in the D. radiodurans cytosol, peptides interacted synergistically with Mn2+ and orthophosphate, and preserved the activity of large, multimeric enzymes exposed to 50,000 Gy, conditions which obliterated DNA. When applied ex vivo, the D. radiodurans ultrafiltrate protected Escherichia coli cells and human Jurkat T cells from extreme cellular insults caused by ionizing radiation. By establishing that Mn2+-metabolite complexes of D. radiodurans specifically protect proteins against indirect damage caused by gamma-rays delivered in vast doses, our findings provide the basis for a new approach to radioprotection and insight into how surplus Mn budgets in cells combat reactive oxygen species.
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