Takatsuka Yumiko, Kamio Yoshiyuki
Laboratory of Applied Microbiology, Department of Microbial Biotechnology, Graduate School of Agricultural Science, Tohoku University, Sendai, Japan.
Biosci Biotechnol Biochem. 2004 Jan;68(1):1-19. doi: 10.1271/bbb.68.1.
The wild type of Selenomonas ruminantium subsp. lactilytica, which is a strictly anaerobic, Gram-negative bacterium isolated from sheep rumen, requires one of the normal saturated volatile fatty acids with 3 to 10 carbon atoms for its growth in a glucose medium; however, no such obligate requirement of fatty acid is observed when the cells are grown in a lactate medium. This bacterium is characterized by a unique structure of the cell envelope and a novel lysine decarboxylase and its regulatory protein. In the first part of this article, we will refer to the chemical structure of phospholipid and lipopolysaccharide in the cell membranes of this bacterium compared with that from the general Gram-negative bacteria for understanding their biological functions. S. ruminantium has neither free nor bound forms of Braun lipoprotein which plays an important role of the maintenance of the structural integrity of the cell surface in general Gram-negative bacteria. However, S. ruminantium has cadaverine, which links covalently to the peptidoglycan as a pivotal constituent for the cell division. In the second part of this article, we will refer to the chemical structure of the cadaverine-containing peptidoglycan, its biosynthesis, and the biological function. In the third part of this article, we will depict the molecular cloning of the genes encoding S. ruminanitum lysine decarboxylase (LDC) and its regulatory protein of 22-kDa (22-kDa protein; P22) which has similar characteristics to that of antizyme of ornithine decarboxylase in eukaryotic cells, and the molecular dissection of these proteins for understanding the regulation of cadaverine biosynthesis. Finally, we will illustrate a proposed structure of the cell envelope, a processes of biosynthesis of the cadaverine-containing peptidoglycan layer, and the LDC degradation mechanism in S. ruminantium, on the basis of the analyses of the cell envelope components, the results from the in vitro experiments on the biosynthesis of the peptidoglycan layer, and the current status of the knowledge on LDC and P22 in this organism.
反刍月形单胞菌乳酸亚种的野生型是一种从绵羊瘤胃中分离出的严格厌氧革兰氏阴性菌，在葡萄糖培养基中生长时需要一种含3至10个碳原子的正常饱和挥发性脂肪酸；然而，当细胞在乳酸培养基中生长时，未观察到对脂肪酸的这种绝对需求。该细菌的特征在于其独特的细胞膜结构以及一种新型赖氨酸脱羧酶及其调节蛋白。在本文的第一部分，我们将比较该细菌细胞膜中磷脂和脂多糖的化学结构与一般革兰氏阴性菌的相应结构，以了解它们的生物学功能。反刍月形单胞菌既没有游离形式也没有结合形式的布劳恩脂蛋白，而布劳恩脂蛋白在一般革兰氏阴性菌中对维持细胞表面结构完整性起着重要作用。然而，反刍月形单胞菌有尸胺，它作为细胞分裂中的关键成分与肽聚糖共价连接。在本文的第二部分，我们将介绍含尸胺肽聚糖的化学结构、其生物合成以及生物学功能。在本文的第三部分，我们将描述编码反刍月形单胞菌赖氨酸脱羧酶（LDC）及其22 kDa调节蛋白（22 kDa蛋白；P22）的基因的分子克隆，该调节蛋白与真核细胞中鸟氨酸脱羧酶的抗酶具有相似特征，并对这些蛋白质进行分子剖析以了解尸胺生物合成的调控。最后，基于对细胞膜成分的分析、肽聚糖层生物合成的体外实验结果以及该生物体中LDC和P22的现有知识状况，我们将阐述反刍月形单胞菌细胞膜的推测结构、含尸胺肽聚糖层的生物合成过程以及LDC降解机制。
