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词条 R bodies
释义

  1. Morphology, assembly, and extension

  2. Function

  3. References

R bodies (from refractile bodies, also R-bodies) are polymeric protein inclusions formed inside the cytoplasm of bacteria.[1] Initially discovered in kappa particles, bacterial endosymbionts of the ciliate Paramecium, R bodies (and genes encoding them) have since been discovered in a variety of taxa.[2]

Morphology, assembly, and extension

At neutral pH, type 51 R bodies resemble a coil of ribbon approximately 500 nm in diameter and approximately 400 nm deep.[1] Encoded by a single operon containing four open reading frames,[3][4] R bodies are formed from two small structural proteins, RebA and RebB.[5] A third protein, RebC, is required for the covalent assembly of these two structural proteins into higher-molecular weight products, visualized as a ladder on an SDS-PAGE gel.[5]

At low pH, Type 51 R bodies undergo a dramatic structural rearrangement. Much like a paper yo-yo, the ribbon extends (from the center) to form hollow tube with pointed ends that can reach up to 20μm in length.[6]

Other types of R bodies from different bacterial species vary in their size, ribbon morphology, and triggers for extension.[1]

Function

When kappa particles shed from a killer paramecium are ingested, R bodies extend within the acidic food vacuole of the predatory paramecium, distending and rupturing the membrane.[7] This liberates the contents of the food vacuole into the cytoplasm of the paramecium.[7] While feeding kappa particles to sensitive paramecium results in the death of paramecium, feeding purified R bodies or R bodies recombinantly expressed in E. coli is not toxic.[3][8] Thus, R bodies are thought to function as a toxin delivery system.

R bodies are also capable of rupturing E. coli spheroplasts, demonstrating that they can rupture membranes in a foreign context, and they can be engineered to extend at a variety of different pH levels.[9]

References

1. ^1 2 {{Cite journal|last=Pond|first=F R|last2=Gibson|first2=I|last3=Lalucat|first3=J|last4=Quackenbush|first4=R L|date=1989-03-01|title=R-body-producing bacteria.|journal=Microbiological Reviews|volume=53|issue=1|pages=25–67|issn=0146-0749|pmc=372716|pmid=2651865}}
2. ^{{Cite journal|last=Raymann|first=Kasie|last2=Bobay|first2=Louis-Marie|last3=Doak|first3=Thomas G.|last4=Lynch|first4=Michael|last5=Gribaldo|first5=Simonetta|date=2013-03-01|title=A genomic survey of Reb homologs suggests widespread occurrence of R-bodies in proteobacteria|journal=G3: Genes, Genomes, Genetics|volume=3|issue=3|pages=505–516|doi=10.1534/g3.112.005231|issn=2160-1836|pmc=3583457|pmid=23450193}}
3. ^1 {{Cite journal|last=Kanabrocki|first=J. A.|last2=Quackenbush|first2=R. L.|last3=Pond|first3=F. R.|date=1986-10-01|title=Organization and expression of genetic determinants for synthesis and assembly of type 51 R bodies|journal=Journal of Bacteriology|volume=168|issue=1|pages=40–48|issn=0021-9193|pmc=213417|pmid=3759909|doi=10.1128/jb.168.1.40-48.1986}}
4. ^{{Cite journal|last=Jeblick|first=Jörn|last2=Kusch|first2=Jürgen|date=2005-02-01|title=Sequence, transcription activity, and evolutionary origin of the R-body coding plasmid pKAP298 from the intracellular parasitic bacterium Caedibacter taeniospiralis|journal=Journal of Molecular Evolution|volume=60|issue=2|pages=164–173|doi=10.1007/s00239-004-0002-2|issn=0022-2844|pmid=15785846}}
5. ^1 {{Cite journal|last=Heruth|first=D. P.|last2=Pond|first2=F. R.|last3=Dilts|first3=J. A.|last4=Quackenbush|first4=R. L.|date=1994-06-01|title=Characterization of genetic determinants for R body synthesis and assembly in Caedibacter taeniospiralis 47 and 116|journal=Journal of Bacteriology|volume=176|issue=12|pages=3559–3567|issn=0021-9193|pmc=205544|pmid=8206833|doi=10.1128/jb.176.12.3559-3567.1994}}
6. ^{{Cite journal|last=Preer|first=John R.|last2=Hufnagel|first2=Linda A.|last3=Preer|first3=Louise B.|date=1966-04-01|title=Structure and behavior of R bodies from killer paramecia|url=http://www.sciencedirect.com/science/article/pii/S0022532066801004|journal=Journal of Ultrastructure Research|volume=15|issue=1|pages=131–143|doi=10.1016/S0022-5320(66)80100-4|pmid=5936490}}
7. ^1 {{Cite journal|last=Mueller|first=Jo Anne|date=1965-12-01|title=Vitally stained kappa in Paramecium aurelia|journal=Journal of Experimental Zoology|language=en|volume=160|issue=3|pages=369–372|doi=10.1002/jez.1401600314|pmid=4160786|issn=1097-010X}}
8. ^{{Cite journal|last=Schrallhammer|first=Martina|last2=Galati|first2=Stefano|last3=Altenbuchner|first3=Josef|last4=Schweikert|first4=Michael|last5=Görtz|first5=Hans-Dieter|last6=Petroni|first6=Giulio|date=2012-11-01|title=Tracing the role of R-bodies in the killer trait: absence of toxicity of R-body producing recombinant E. coli on paramecia|journal=European Journal of Protistology|volume=48|issue=4|pages=290–296|doi=10.1016/j.ejop.2012.01.008|issn=1618-0429|pmid=22356923}}
9. ^{{Cite journal|last=Polka|first=Jessica K.|last2=Silver|first2=Pamela A.|date=2016-04-15|title=A Tunable Protein Piston That Breaks Membranes to Release Encapsulated Cargo|journal=ACS Synthetic Biology|volume=5|issue=4|pages=303–311|doi=10.1021/acssynbio.5b00237|pmid=26814170}}

5 : Cell biology|Cell anatomy|Protein complexes|Bacteriology|Biotechnology
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