Kanabrocki J A, Quackenbush R L, Pond F R
J Bacteriol. 1986 Oct;168(1):40-8. doi: 10.1128/jb.168.1.40-48.1986.
Type 51 R bodies are produced by all bacterial endosymbionts (Caedibacter taeniospiralis) of Paramecium tetraurelia that confer the hump-killer trait upon their hosts. Type 51 R-body synthesis by C. taeniospiralis is required for expression of the hump-killer trait. The genetic determinants for type 51 R-body synthesis by C. taeniospiralis 47 have been cloned and expressed in Escherichia coli. In this communication we describe three species of polypeptides required for R-body synthesis and the organization of their genetic determinants. Each polypeptide species is controlled by a separate gene that is expressed as an independent transcriptional unit possessing regulatory signals that are recognized by E. coli. Two polypeptide species of 10 and 18 kilodaltons are required for R-body synthesis but apparently are not structural subunits. The third polypeptide species (13 kilodaltons) is the major structural subunit. R-body assembly involves polymerization reactions that result in high-molecular-mass polypeptide complexes, primarily composed of the 13-kilodalton polypeptide species, that appear to be the result of covalent cross-linking between structural subunits. The results presented here have been suggested to apply to the assembly and structure of all type 51 R bodies, but not necessarily to other R-body types.
51型R体由四膜虫的所有细菌内共生体（带螺旋体凯氏杆菌）产生，这些内共生体赋予宿主驼峰杀手特性。带螺旋体凯氏杆菌合成51型R体是表达驼峰杀手特性所必需的。带螺旋体凯氏杆菌47合成51型R体的遗传决定因素已被克隆并在大肠杆菌中表达。在本通讯中，我们描述了R体合成所需的三种多肽及其遗传决定因素的组织方式。每种多肽由一个单独的基因控制，该基因作为一个独立的转录单元表达，具有可被大肠杆菌识别的调控信号。R体合成需要10千道尔顿和18千道尔顿的两种多肽，但显然它们不是结构亚基。第三种多肽（13千道尔顿）是主要的结构亚基。R体组装涉及聚合反应，产生高分子量的多肽复合物，主要由13千道尔顿的多肽组成，这似乎是结构亚基之间共价交联的结果。这里呈现的结果被认为适用于所有51型R体的组装和结构，但不一定适用于其他类型的R体。
