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Bacterial microcompartments are widespread bacterial organelles that are made of a protein shell that surrounds and encloses various enzymes.[1] These compartments are typically about 100-200 nanometres across and made of interlocking proteins.[2] They do not contain lipids since they are not surrounded by a membrane. Protein-enclosed compartments are also found in eukaryotes, such as the mysterious vault complex.[3]

Contents

Protein families forming the microcompartment shell

The shells of diverse microcompartments are composed of members of three protein families: the BMC domain protein family, the inconsistently named CsoS4 / CcmL / EutN / OrfAB family, and the encapsulins/linocin-like proteins.

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The BMC protein family

In microcompartment shells that have been studied, the major constituents are proteins belonging to the Bacterial Micro-Compartment (BMC) family. The crystal structures of a number of BMC proteins have been determined and invariably reveal assembly into cyclical hexamers with a small pore in the center.

The CsoS4 family

Recent structures have revealed either a pentameric or hexameric structure in this family. In icosahedral or quasi-icosahedral carboxysomes, it is likely that the pentameric form is positioned at the vertices.

Encapsulins

Encapsulins are a large and widely-distributed family of proteins and are present in most bacteria and have been identified in Candidatus methanoregula, a species of archaea. They were originally called linocin-like proteins and thought to be a group of bacterial antibiotics, since they showed bacteriostatic activity in culture. However, structural analysis showed these to form a spherical nanocompartment that contains enzymes involved in the defenses against oxidative stress.[3]

Types

A recent survey indicated seven different metabolic systems encapsulated by microcompartment shells.[1] Three are characterized:

Carboxysomes

Carboxysomes encapsulate RuBisCo and carbonic anhydrase in carbon-fixing bacteria as part of a carbon concentrating mechanism.[4]

Pdu microcompartments

Some bacteria can used 1,2-propanediol as a carbon source. They express a microcompartment to encapsulate a number of enzymes used in this pathway.[5] The Pdu compartment is constructed by a set of 21 genes in a single chromosomal locus. These genes are sufficient for assembly of the microcompartment since they can be transferred between bacteria and will produce a functional structure in the recipient.[6]

Eut microcompartments

EUT microcompartments are proposed to form in Salmonella species, and may be involved in the metabolism of ethanolamine.[7]

See also

References

  1. ^ a b Bobik, T. A. (2007). "Bacterial Microcompartments" (PDF). Microbe (Am Soc Microbiol) 2: 25–31. http://www.asm.org/ASM/files/ccLibraryFiles/Filename/000000002765/znw00107000025.pdf.  
  2. ^ Yeates TO, Kerfeld CA, Heinhorst S, Cannon GC, Shively JM (August 2008). "Protein-based organelles in bacteria: carboxysomes and related microcompartments". Nat. Rev. Microbiol. 6 (9): 681–691. doi:10.1038/nrmicro1913. PMID 18679172.  
  3. ^ a b Sutter M, Boehringer D, Gutmann S, et al. (August 2008). "Structural basis of enzyme encapsulation into a bacterial nanocompartment". Nat. Struct. Mol. Biol. 15: 939–947. doi:10.1038/nsmb.1473. PMID 18758469.  
  4. ^ Badger MR, Price GD (February 2003). "CO2 concentrating mechanisms in cyanobacteria: molecular components, their diversity and evolution". J. Exp. Bot. 54 (383): 609–22. doi:10.1093/jxb/erg076. PMID 12554704. http://jexbot.oxfordjournals.org/cgi/pmidlookup?view=long&pmid=12554704.  
  5. ^ Sampson EM, Bobik TA (April 2008). "Microcompartments for B12-dependent 1,2-propanediol degradation provide protection from DNA and cellular damage by a reactive metabolic intermediate". J. Bacteriol. 190 (8): 2966–71. doi:10.1128/JB.01925-07. PMID 18296526.  
  6. ^ Parsons JB, Dinesh SD, Deery E, et al. (May 2008). "Biochemical and structural insights into bacterial organelle form and biogenesis". J. Biol. Chem. 283 (21): 14366–75. doi:10.1074/jbc.M709214200. PMID 18332146.  
  7. ^ Penrod JT, Roth JR (April 2006). "Conserving a volatile metabolite: a role for carboxysome-like organelles in Salmonella enterica". J. Bacteriol. 188 (8): 2865–74. doi:10.1128/JB.188.8.2865-2874.2006. PMID 16585748. PMC 1447003. http://jb.asm.org/cgi/pmidlookup?view=long&pmid=16585748.  

External links


Simple English

Bacterial microcompartments are structures inside bacteria. They are made of a protein shell which surrounds and encloses various enzymes.[1] They are similar to eukaryotic cell organelles, but do not have plasma membranes. They do not contain lipids.[2]

These compartments are typically about 100-200 nanometres across and made of interlocking proteins.[3]

Protein-enclosed compartments are also found in eukaryotes, such as enzyme encapsulation.[4]

References

  1. Bobik T.A. (2007). "Bacterial microcompartments" (PDF). Microbe (Am Soc Microbiol) 2: 25–31. http://www.asm.org/ASM/files/ccLibraryFiles/Filename/000000002765/znw00107000025.pdf. 
  2. Sutter M, Boehringer D, Gutmann S, et al. (August 2008). [Expression error: Unexpected < operator "Structural basis of enzyme encapsulation into a bacterial nanocompartment"]. Nat. Struct. Mol. Biol. 15: 939–947. doi:10.1038/nsmb.1473. PMID 18758469. 
  3. Yeates TO, Kerfeld CA, Heinhorst S, Cannon GC, Shively JM (August 2008). [Expression error: Unexpected < operator "Protein-based organelles in bacteria: carboxysomes and related microcompartments"]. Nat. Rev. Microbiol. 6 (9): 681–691. doi:10.1038/nrmicro1913. PMID 18679172. 
  4. Kedersha NL, Miquel MC, Bittner D, Rome LH (1990). [Expression error: Unexpected < operator "Vaults. II. Ribonucleoprotein structures are highly conserved among higher and lower eukaryotes."]. J Cell Biol 110 (4): 895–901. doi:10.1083/jcb.110.4.895. PMID 1691193. 

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