Structures of chaperonins from an intracellular symbiont and their functional expression in Escherichia coli groE mutants.
An intracellular symbiont harbored by the aphid bacteriocyte, a specialized fat body cell, synthesizes in vivo substantially only one protein, symbionin, which is a member of the chaperonin-60 family of molecular chaperones. Nucleotide sequence determination of the symbionin region of the endosymbiont genome revealed that it contains the two-cistron operon sym. Just like the Escherichia coli groE operon, the sym operon was dually led by a heat shock and an ordinary promoter sequence. According to the nucleotide sequence, symbionin was 85.5% identical to GroEL of E. coli at the amino acid sequence level. SymS, another protein encoded in the sym operon, which is a member of chaperonin-10, was 79.6% identical to GroES. Complementation experiments with E. coli groE mutants showed that the chaperonin-10 and chaperonin-60 genes from the endosymbiont are expressed in E. coli and that they can function as molecular chaperones together with endogenous GroEL and GroES, respectively.
Ohtaka
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Zoological Institute, Faculty of Science, University of Tokyo, Japan.
Nakamura
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Ishikawa
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D000595:Amino Acid Sequence; D000818:Animals; D001042:Aphids / Q000382:microbiology*; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics*; D001483:Base Sequence; D018835:Chaperonin 10; D018834:Chaperonin 60; D018833:Chaperonins; D003001:Cloning, Molecular; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D005816:Genetic Complementation Test; D006360:Heat-Shock Proteins / Q000235:genetics; D006860:Hydrogen Bonding; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D009876:Operon; D011401:Promoter Regions, Genetic; D011506:Proteins / Q000737:chemistry / Q000235:genetics*; D015183:Restriction Mapping; D016415:Sequence Alignment; D013559:Symbiosis
D001426:Bacterial Proteins; D018835:Chaperonin 10; D018834:Chaperonin 60; D006360:Heat-Shock Proteins; D011506:Proteins; C044322:SymL protein, Bacteria; D018833:Chaperonins