Cerletti Micaela, Martínez María J, Giménez María I, Sastre Diego E, Paggi Roberto A, De Castro Rosana E
Instituto de Investigaciones Biológicas, Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Mar del Plata, Mar del Plata, Argentina.
Environ Microbiol. 2014 Jun;16(6):1779-92. doi: 10.1111/1462-2920.12385. Epub 2014 Feb 20.
Although homologs of the ATP-dependent Lon protease exist in all domains of life, the relevance of this protease in archaeal physiology remains a mystery. In this study, we have constructed and phenotypically characterized deletion and conditional lon mutants in the model haloarchaeon Haloferax volcanii to elucidate the role of the unusual membrane-bound LonB protease in archaea. Hvlon could be deleted from the chromosome only when a copy of the wild type gene was provided in trans suggesting that Lon is essential for survival in this archaeon. Successful complementation of the lethal phenotype of ΔHvlon was attained by expression of the heterologous protease gene Nmlon from the haloalkaliphilic archaeon Natrialba magadii, meaning that the biological function of Lon is conserved in these organisms. Suboptimal cellular levels of Lon protein affected growth rate, cell shape, cell pigmentation, lipid composition and sensitivity to various antibiotics. The contents of bacterioruberins and some polar lipids were increased in the lon mutants suggesting that Lon is linked to maintenance of membrane lipid balance which likely affects cell viability in this archaeon. The phenotypes associated to a membrane-bound LonB protease mutant were examined for the first time providing insight on the relevance of this protease in archaeal physiology.
尽管依赖ATP的Lon蛋白酶的同源物存在于生命的所有领域，但这种蛋白酶在古菌生理学中的相关性仍然是个谜。在这项研究中，我们构建了模式嗜盐古菌沃氏嗜盐栖热菌中的缺失型和条件型lon突变体，并对其进行了表型特征分析，以阐明这种不寻常的膜结合LonB蛋白酶在古菌中的作用。只有当野生型基因的一个拷贝通过反式提供时，Hvlon才能从染色体上删除，这表明Lon对于这种古菌的生存至关重要。通过表达来自嗜盐碱古菌马氏嗜盐碱杆菌的异源蛋白酶基因Nmlon，成功地互补了ΔHvlon的致死表型，这意味着Lon的生物学功能在这些生物体中是保守的。Lon蛋白的细胞水平次优会影响生长速率、细胞形状、细胞色素沉着、脂质组成以及对各种抗生素的敏感性。lon突变体中细菌红素和一些极性脂质的含量增加，这表明Lon与膜脂平衡的维持有关，而膜脂平衡可能会影响这种古菌的细胞活力。首次研究了与膜结合LonB蛋白酶突变体相关的表型，为这种蛋白酶在古菌生理学中的相关性提供了见解。
