Aksoy S
Department of Internal Medicine, Yale University School of Medicine, New Haven, Connecticut 06510, USA.
Insect Mol Biol. 1995 Feb;4(1):23-9. doi: 10.1111/j.1365-2583.1995.tb00004.x.
Based on 16S rDNA sequence comparison, intracellular mycetome-associated endosymbionts (P-endosymbionts) of tsetse flies (Diptera: Glossinidae) form a distinct lineage within the gamma-3 subdivision of proteobacteria, related to the free-living bacterium Escherichia coli, midgut S-endosymbionts of various insects including tsetse flies, and to the P-endosymbiont lineage of aphids, Buchnera aphidicola. Gene organization and expression of several loci in intracellular microorganisms have revealed differences from free-living bacteria. This study analyses two of these characteristics in tsetse endosymbionts; the copy number and gene organization of rDNA operations and the nature of the abundant protein(s) synthesized by these microorganisms. Results indicate that Glossina morsitans morsitans S-endosymbionts have multiple (seven) rDNA operons coding for 16S (rrs) followed by 23S (rrl) gene sequences, whereas tsetse P-endosymbionts have a single, similarly organized rDNA operon. In tsetse mycetocytes in vitro, P-endosymbionts synthesize a predominant protein of 60 kDa in size (p60) which by Western blot analysis shows immunological cross-reactivity with the abundant 63 kDa (p63) protein of B. aphidicola. p63 (also referred to as symbionin) has been characterized as a molecular chaperone, structurally and functionally similar to the groEL protein of E. coli. Under in vitro conditions, tsetse S-endosymbionts synthesize high levels of a similarly-sized protein that cross-reacts with p63 chaperonin. Antisera against the tsetse p60 protein also recognizes p63 protein of B. aphidicola, suggesting that the abundant tsetse endosymbiont protein is a chaperonin.
基于16S rDNA序列比较，采采蝇（双翅目：舌蝇科）细胞内与菌瘤相关的内共生体（P-内共生体）在变形菌纲γ-3亚群中形成一个独特的谱系，与自由生活的细菌大肠杆菌、包括采采蝇在内的各种昆虫的中肠S-内共生体以及蚜虫内共生体谱系布赫纳氏菌相关。细胞内微生物中几个基因座的基因组织和表达已显示出与自由生活细菌的差异。本研究分析了采采蝇内共生体的两个此类特征；rDNA操纵子的拷贝数和基因组织以及这些微生物合成的丰富蛋白质的性质。结果表明， morsitans morsitans采采蝇的S-内共生体有多个（七个）编码16S（rrs）随后是23S（rrl）基因序列的rDNA操纵子，而采采蝇的P-内共生体有一个单一的、组织类似的rDNA操纵子。在体外采采蝇的菌细胞中，P-内共生体合成一种大小为60 kDa的主要蛋白质（p60），通过蛋白质印迹分析显示其与布赫纳氏菌丰富的63 kDa（p63）蛋白质具有免疫交叉反应性。p63（也称为共生蛋白）已被鉴定为一种分子伴侣，在结构和功能上与大肠杆菌的groEL蛋白相似。在体外条件下，采采蝇的S-内共生体合成高水平的大小类似的蛋白质，该蛋白质与p63伴侣蛋白发生交叉反应。针对采采蝇p60蛋白质的抗血清也识别布赫纳氏菌的p63蛋白质，表明采采蝇丰富的内共生体蛋白质是一种伴侣蛋白。
