Karlin S, Mrazek J
Department of Mathematics, Stanford University, Stanford, CA 94305-2125, USA.
Proc Natl Acad Sci U S A. 2001 Apr 24;98(9):5240-5. doi: 10.1073/pnas.081077598. Epub 2001 Apr 10.
Predicted highly expressed (PHX) and putative alien genes determined by codon usages are characterized in the genome of Deinococcus radiodurans (strain R1). Deinococcus radiodurans (DEIRA) can survive very high doses of ionizing radiation that are lethal to virtually all other organisms. It has been argued that DEIRA is endowed with enhanced repair systems that provide protection and stability. However, predicted expression levels of DNA repair proteins with the exception of RecA tend to be low and do not distinguish DEIRA from other prokaryotes. In this paper, the capability of DEIRA to resist extreme doses of ionizing and UV radiation is attributed to an unusually high number of PHX chaperone/degradation, protease, and detoxification genes. Explicitly, compared with all current complete prokaryotic genomes, DEIRA contains the greatest number of PHX detoxification and protease proteins. Other sources of environmental protection against severe conditions of UV radiation, desiccation, and thermal effects for DEIRA are the several S-layer (surface structure) PHX proteins. The top PHX gene of DEIRA is the multifunctional tricarboxylic acid (TCA) gene aconitase, which, apart from its role in respiration, also alerts the cell to oxidative damage.
通过密码子使用情况确定的预测高表达（PHX）和假定的外来基因在耐辐射球菌（菌株R1）的基因组中得到了表征。耐辐射球菌（DEIRA）能够在极高剂量的电离辐射下存活，而这种辐射对几乎所有其他生物都是致命的。有人认为，DEIRA拥有增强的修复系统，能提供保护和稳定性。然而，除RecA外，DNA修复蛋白的预测表达水平往往较低，且这并不能将DEIRA与其他原核生物区分开来。在本文中，DEIRA抵抗极端剂量电离辐射和紫外线辐射的能力归因于异常大量的PHX伴侣/降解、蛋白酶和解毒基因。具体而言，与目前所有完整的原核生物基因组相比，DEIRA含有数量最多的PHX解毒和蛋白酶蛋白。DEIRA抵御紫外线辐射、干燥和热效应等恶劣环境条件的其他来源是几种S层（表面结构）PHX蛋白。DEIRA的顶级PHX基因是多功能三羧酸（TCA）基因乌头酸酶，它除了在呼吸作用中的作用外，还能使细胞对氧化损伤产生警觉。
