Morimoto Takuya, Loh Pek Chin, Hirai Tomohiro, Asai Kei, Kobayashi Kazuo, Moriya Shigeki, Ogasawara Naotake
Department of Microbial Cell Biology, Graduate school of Biological Sciences, Nara Institute of Science and Technology, 8916-5, Takayama, Ikoma, Nara 630-0101, Japan1.
Microbiology (Reading). 2002 Nov;148(Pt 11):3539-3552. doi: 10.1099/00221287-148-11-3539.
GTP-binding proteins are found in all domains of life and are involved in various essential cellular processes. With the recent explosion of available genome sequence data, a widely distributed bacterial subfamily of GTP-binding proteins was discovered, represented by the Escherichia coli Era and the Bacillus subtilis Obg proteins. Although only a limited number of the GTP-binding proteins belonging to the subfamily have been experimentally characterized, and their function remains unknown, the available data suggests that many of them are essential to bacterial growth. When the complete genomic sequence of B. subtilis was surveyed for genes encoding GTP-binding proteins of the Era/Obg family, nine such genes were identified. As a first step in elucidating the functional networks of those nine GTP-binding proteins, data presented here indicates that six of them are essential for B. subtilis viability. Additionally, it is shown that the six essential proteins are able to specifically bind GTP and GDP in vitro. Experimental depletion of the essential GTP-binding proteins was examined in the context of cell morphology and chromosome replication, and it was found that two proteins, Bex and YqeH, appeared to participate in the regulation of initiation of chromosome replication. Collectively, these results suggest that members of the GTP-binding Era/Obg family are important proteins with precise, yet still not fully understood, roles in bacterial growth and viability.
GTP结合蛋白存在于生命的所有领域，参与各种重要的细胞过程。随着近期可用基因组序列数据的激增，人们发现了一个广泛分布的GTP结合蛋白细菌亚家族，以大肠杆菌Era和枯草芽孢杆菌Obg蛋白为代表。尽管属于该亚家族的GTP结合蛋白只有少数经过了实验表征，其功能仍不清楚，但现有数据表明，其中许多蛋白对细菌生长至关重要。在对枯草芽孢杆菌的完整基因组序列进行编码Era/Obg家族GTP结合蛋白的基因调查时，鉴定出了9个这样的基因。作为阐明这9个GTP结合蛋白功能网络的第一步，本文给出的数据表明其中6个对枯草芽孢杆菌的生存能力至关重要。此外，研究表明这6个必需蛋白在体外能够特异性结合GTP和GDP。在细胞形态和染色体复制的背景下，对必需的GTP结合蛋白进行了实验性消耗研究，发现有两个蛋白Bex和YqeH似乎参与了染色体复制起始的调控。总体而言，这些结果表明，GTP结合Era/Obg家族的成员是重要的蛋白，在细菌生长和生存能力方面发挥着精确但仍未完全了解的作用。
