• 생명과학회지
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• 제6권3호
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• pp.213-218
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• 1996

대장균의 GroEL과 상동성을 가지는 symbionin이 진딧물의 세포내 곤생미생물에서 유일하게 생산된다. 이것은 in vitro와 in vivo에서 moecular chaperone 활성을 가지는 것과 함께 자가인산화(autophosphory-lation)와 인산기전이효소(phosphotransferase)의 활성에 의해서 고에너지 인산기를 다른 곳에 줄 수 있다. Symbionin은 two component pathway의 센서분자의 역할을 하며, 지금까지 알려진 것과는 다른 성질을 가진 protein Kinase이다.

• Animal cells and systems
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• 제5권3호
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• pp.163-177
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• 2001

Most, if not all, aphids harbor intracellular bacterial symbionts, called Buchnera, in their bacteriocytes, huge cells differentiated for this purpose. The association between Buchnera and aphids is so intimate, mutualistic and obligate that neither of them can any longer reproduce independently. Buchnera are vertically transmitted through generations of the host insects. Evidence suggests that Buchnera were acquired by a common ancestor of aphids 160-280 million years ago, and have been diversified, since then, in parallel with their aphid hosts. Molecular phylogenetic analyses indicate that Buchnera belong to the g subdivision of the Proteobacteria. Although Buchnera are close relatives of Escherichia coli, they contain move than 100 genomic copies per cell, and their genome size is only one seventh that of E. coli. The complete genome sequence of Buchnera revealed that their gene repertoire is quite different from those of parasitic bacteria such as Mycoplasma, Rickettsia and Chlamydia, though their genome sizes have been reduced to a similar extent. Whereas these parasitic bacteria have lost most genes for the biosynthesis of amino acids, Buchnera retain many of them. In particular, Buchnera's gene repertoire is characteristic in the richness of the genes for the biosynthesis of essential amino acids that the eukaryotic hosts are not able to synthesize, reflecting a nutritional role played by these symbionts. Buchnera, when housed in the bacteriocyte, selectively synthesize a large amount of symbionin, which is a homolog of GroEL, the major stress protein of E. coli. Symbionin not only functions as molecular chaperone, like GroEL, but also has evolutionarily acquired the phosphotransferase activity through amino acid substitutions. Aphids usually profit from Buchnera's fuction as a nutritional supplier and, when faced with an emergency, consume the biomass of Buchnera cells as nutrient reserves.