カルボキシソーム
With a small structure body of the protein which accumulated ribulose-1,5-screw phosphoric acid carboxylase (ルビスコ), there is it to the cytoplasm of a cyanobacterium and some chemoautotrophy bacteria. ルビスコ accumulates it in the inside of カルボキシソーム and, as polyhedron structure covered to special husk protein, is observed with an electron microscope well. The role converts a bicarbonate ion concentrated by cytoplasm into CO2 locally and supplies it to ルビスコ and is to help with a carbon dioxide fixation reaction.
Table of contents
History
In 1956, I was discovered as a polyhedron-like structure body in a cell of cyanobacterium Phormidium uncinatum. Because it was isolated from chemoautotrophy bacteria Halothiobacillus neapolitanus in 1973 and included ルビスコ, I was named カルボキシソーム.
Distribution
I am distributed over photosynthesizing almost all cyanobacteria and some chemoautotrophy bacteria which assume ルビスコ a main CO2 fixation enzyme (mainly friend Halothiobacillus, Thiobacillus, Thiomonas, Acidithiobacillus, Nitrobacter, Nirosomonas of the proteobacterium). With the report to be カルボキシソーム rather than pyrenoid as for the protein structure body which there is to a chloroplast of primitive alga Cyanophora paradoxa of the truth nucleus [1].
Structure
With polyhedron structure of size 80-140nm, it is surrounded in the layer of the husk protein (cf. image) of thickness 3-4nm by husk of the protein and ルビスコ in the inside. In addition, the carbonic anhydrase (it is said with the carbonic anhydrase) is included, too, but the local existence does not become clear [2]; [3].
Physiological role
The cyanobacterium accumulates bicarbonate ion (HCO3–) in the high density to cytoplasm with strong concentration mechanism carbonate in a light place. The carbonic anhydrase in カルボキシソーム converts a bicarbonate ion into carbon dioxide and supplies carbon dioxide to close-by ルビスコ. I cannot concentrate carbon dioxide as the dissolved gas in a cell, but can concentrate the bicarbonate ion in a cell. However, a substrate of ルビスコ is carbon dioxide and cannot fix the bicarbonate ion. カルボキシソーム overcomes such a contradiction and converts a bicarbonate ion concentrated by cytoplasm into carbon dioxide locally and is structure to supply it to ルビスコ. Therefore, I photosynthesize in hypocapnia gas density, and カルボキシソーム cannot multiply when I produce variation.
Classification
I am classified in two kinds by a component. α-カルボキシソーム is distributed over chemoautotrophy bacteria and the α-cyanobacterium (including Prochlorococcus), and β-カルボキシソーム is distributed over the β-cyanobacterium (including Synechocystis). The gene encoding α-カルボキシソーム becomes the bundle, but the gene of β-カルボキシソーム is divided into some clusters. In addition, this difference is associated with the system of ルビスコ. In other words, in α-カルボキシソーム, β-カルボキシソーム has ルビスコ of Form IB in ルビスコ of Form IA.
Allied with the pyrenoid
The algal pyrenoid accumulating ルビスコ is said to be a kind of homologue. However, having surface husk protein or not is not clear.
Similar structure body
When 資化 does ethanolamine and propanediol in an aversion state to Salmonella and Escherichia coli, a structure body similar to カルボキシソーム is formed to cytoplasm. The composition of this structure body does not become clear, but it is thought with an associated structure body because there is a gene showing husk protein and homogeny of カルボキシソーム in ethanolamine and propanediol 資化 operon. However, these bacteria do not have ルビスコ, and carbon dioxide fixation does not have the direct relations, but the function is still unknown.
Documents
- ^ Fathinejad S, Steiner JM, Reipert S, Marchetti M, Allmaier G, Burey SC, Ohnishi N, Fukuzawa H, Löffelhardt W, Bohnert HJ (2008). "A carboxysomal carbon-concentrating mechanism in the cyanelles of the 'coelacanth' of the algal world, Cyanophora paradoxa?." Physiol. Plant. 133 (1): 27–32. PMID 18248510.
- ^ Shively JM, van Keulen G, Meijer WG (1998). "Something from almost nothing: carbon dioxide fixation in chemoautotrophs." Annual Review Microbiol. It is 191–230. 52 PMID 9891798.
- ^ Yeates TO, Kerfeld CA, Heinhorst S, Cannon GC, Shively JM (2008). "Protein-based organelles in bacteria: carboxysomes and related microcompartments." Nature Review Microbiol. 6 (9): 681–91. PMID 18679172.
This article is taken from the Japanese Wikipedia カルボキシソーム
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