タンパク質複合体、タンパク複合体

WordNet

complicated in structure; consisting of interconnected parts; "a complex set of variations based on a simple folk melody"; "a complex mass of diverse laws and customs"
a compound described in terms of the central atom to which other atoms are bound or coordinated (同)coordination_compound
a conceptual whole made up of complicated and related parts; "the complex of shopping malls, houses, and roads created a new town" (同)composite
(psychoanalysis) a combination of emotions and impulses that have been rejected from awareness but still influence a persons behavior
any of a large group of nitrogenous organic compounds that are essential constituents of living cells; consist of polymers of amino acids; essential in the diet of animals for growth and for repair of tissues; can be obtained from meat and eggs and milk and legumes; "a diet high in protein"

PrepTutorEJDIC

『いくつかの部分から成る』,複合の,合成の / 『複雑な』,入りくんだ,こみいった(complicated) / 複合体,合成物 / コンプレックス,複合(抑圧されて心に残った複雑なしこり)
蛋白(たんばく)質

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2014/02/13 08:31:49」(JST)

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Bacillus amyloliquefaciens proteins in a complex

A multiprotein complex (or protein complex) is a group of two or more associated polypeptide chains. If the different polypeptide chains contain different protein domain, the resulting multiprotein complex can have multiple catalytic functions. This is distinct from a multienzyme polypeptide, in which multiple catalytic domains are found in a single polypeptide chain.^[1]

Protein complexes are a form of quaternary structure. Proteins in a protein complex are linked by non-covalent protein–protein interactions, and different protein complexes have different degrees of stability over time. These complexes are a cornerstone of many (if not most) biological processes and together they form various types of molecular machinery that perform a vast array of biological functions. Increasingly, scientists view the cell as composed of modular supramolecular complexes, each of which performs an independent, discrete biological function.^[2]

Through proximity, the speed and selectivity of binding interactions between enzymatic complex and substrates can be vastly improved, leading to higher cellular efficiency. Unfortunately, many of the techniques used to break open cells and isolate proteins are inherently disruptive to such large complexes, so their protein complexes within the cell may be even more widespread than can be detected. Examples include the proteasome for molecular degradation, the metabolon for oxidative energy generation, and the ribosome for protein synthesis. In stable complexes, large hydrophobic interfaces between proteins typically bury surface areas larger than 2500 square angstroms.^[3]

Function[edit]

Protein complex formation sometimes serves to activate or inhibit one or more of the complex members and in this way, protein complex formation can be similar to phosphorylation. Individual proteins can participate in the formation of a variety of different protein complexes. Different complexes perform different functions, and the same complex can perform very different functions that depend on a variety of factors. Some of these factors are:

Which cellular compartment the complex exists in when it is contained
Which stage in the cell cycle the complexes are present
The nutritional status of the cell
Others

Many protein complexes are well understood, particularly in the model organism Saccharomyces cerevisiae (a strain of yeast). For this relatively simple organism, the study of protein complexes is now being performed genome wide and the elucidation of most protein complexes of the yeast is undergoing.

Types of protein complexes[edit]

Obligate vs non-obligate protein complex[edit]

If a protein can form stable crystal structure of its own (without any other associated protein) in vivo, then the complexes formed by such proteins are called "non-obligate protein complex". On the other hand, some proteins can't be found to create a crystal structure alone, but can be found as a part of a protein complex which creates a stable crystal structure. Such protein complexes are called "obligate protein complex".^[4]

Transient vs permanent/stable protein complex[edit]

Transient protein complexes form and break down transiently in vivo, whereas permanent complexes have a relatively long half-life. Typically, the obligate interactions (protein-protein interactions in an obligate complex) are permanent, whereas non-obligate interactions have been found to be either permanent or transient.^[4] Note that there is no clear distinction between obligate and non-obligate interaction, rather there exist a continuum between them which depends on various conditions e.g. pH, protein concentration etc.^[5] However, there are important distinctions between the properties of transient and permanent/stable interactions: stable interactions are highly conserved but transient interactions are far less conserved, interacting proteins on the two sides of a stable interaction have more tendency of being co-expressed than those of a transient interaction (in fact, co-expression probability between two transiently interacting proteins is not higher than two random proteins), and transient interactions are much less co-localized than stable interactions.^[6] Though, transient by nature, transient interactions are very important for cell biology: human interactome is enriched in such interactions, these interactions are the dominating players of gene regulation and signal transduction, and proteins with intrinsically disordered regions (IDR: regions in protein that show dynamic inter-converting structures in the native state) are found to be enriched in transient regulatory and signaling interactions.^[4]

Fuzzy complex[edit]

Fuzzy protein complexes have more than one structural forms or dynamic structural disorder in the bound state.^[7] This means that proteins may not fold completely in either transient or permanent complexes. Consequently, specific complexes can have ambiguous interactions, which vary according to the environmental signals. Hence different ensemble of structures result in different (even opposite) biological functions.^[8] Post-translational modifications, protein interactions or alternative splicing modulate the conformational ensembles of fuzzy complexes, to fine-tune affinity or specificity of interactions. These mechanisms are often used for regulation within the eukaryotic transcription machinery.^[9]

Homomultimeric and heteromultimeric proteins[edit]

The subunits of a multimeric protein may be identical as in a homomultimeric (homooligomeric) protein or different as in a heteromultimeric protein. Many soluble and membrane proteins form homomultimeric complexes in a cell, majority of proteins in the Protein Data Bank are homomultimeric.^[10] Homooligomers are responsible for the diversity and specificity of many pathways, may mediate and regulate gene expression, activity of enzymes, ion channels, receptors, and cell adhesion processes.

The voltage-gated potassium channels in the plasma membrane of a neuron are heteromultimeric proteins composed of four of forty known alpha subunits. Subunits must be of the same subfamily to form the multimeric protein channel. The tertiary structure of the channel allows ions to flow through the hydrophobic plasma membrane. Connexons are an example of a homomultimeric protein composed of six identical connexins. A cluster of connexons forms the gap-junction in two neurons that transmit signals through an electrical synapse.

Determination[edit]

The molecular structure of protein complexes can be determined by experimental techniques such as X-ray crystallography or nuclear magnetic resonance. Increasingly the theoretical option of protein–protein docking is also becoming available. One method that is commonly used for identifying the meomplexes is immunoprecipitation. Recently, Raicu and coworkers developed a method to determine the quaternary structure of protein complexes in living cells. This method is based on the determination of pixel-level Forster resonance energy transfer (FRET) efficiency in conjunction with spectrally resolved two-photon microscope. The distribution of FRET efficiencies are simulated against different models to get the geometry and stoichiometry of the complexes.^[11]

References[edit]

^ Price NC, Stevens L (1999). Fundamentals of enzymology: The cell and molecular biology of catalytic protein. Oxford ; New York: Oxford University Press. ISBN 0-19-850229-X.
^ Hartwell LH, Hopfield JJ, Leibler S, Murray AW (December 1999). "From molecular to modular cell biology". Nature 402 (6761 Suppl): C47–52. doi:10.1038/35011540. PMID 10591225.
^ Pereira-Leal JB, Levy ED, Teichmann SA (March 2006). "The origins and evolution of functional modules: lessons from protein complexes". Philos. Trans. R. Soc. Lond., B, Biol. Sci. 361 (1467): 507–17. doi:10.1098/rstb.2005.1807. PMC 1609335. PMID 16524839.
^ ^a ^b ^c Amoutzias G, Van de Peer Y (2010). Single-Gene and Whole-Genome Duplications and the Evolution of Protein–Protein Interaction Networks. Evolutionary genomics and systems biology. pp. 413–429. doi:10.1002/9780470570418.ch19.
^ Nooren IM, Thornton JM (July 2003). "Diversity of protein-protein interactions". EMBO J. 22 (14): 3486–92. doi:10.1093/emboj/cdg359. PMC 165629. PMID 12853464.
^ Brown KR, Jurisica I (2007). "Unequal evolutionary conservation of human protein interactions in interologous networks". Genome Biol. 8 (5): R95. doi:10.1186/gb-2007-8-5-r95. PMC 1929159. PMID 17535438.
^ Tompa P, Fuxreiter M (January 2008). "Fuzzy complexes: polymorphism and structural disorder in protein-protein interactions". Trends Biochem. Sci. 33 (1): 2–8. doi:10.1016/j.tibs.2007.10.003. PMID 18054235.
^ Fuxreiter M (January 2012). "Fuzziness: linking regulation to protein dynamics". Mol Biosyst 8 (1): 168–77. doi:10.1039/c1mb05234a. PMID 21927770.
^ Fuxreiter M, Simon I, Bondos S (August 2011). "Dynamic protein-DNA recognition: beyond what can be seen". Trends Biochem. Sci. 36 (8): 415–23. doi:10.1016/j.tibs.2011.04.006. PMID 21620710.
^ Hashimoto K, Nishi H, Bryant S, Panchenko AR (June 2011). "Caught in self-interaction: evolutionary and functional mechanisms of protein homooligomerization". Phys Biol 8 (3): 035007. doi:10.1088/1478-3975/8/3/035007. PMC 3148176. PMID 21572178.
^ Raicu V, Stoneman MR, Fung R, Melnichuk M, Jansma DB, Pisterzi LF, Rath S, Fox, M, Wells, JW, Saldin DK (2008). "Determination of supramolecular structure and spatial distribution of protein complexes in living cells.". Nature Photonics 3: 107–113. doi:10.1038/nphoton.2008.291.

External links[edit]

Multiprotein Complexes at the US National Library of Medicine Medical Subject Headings (MeSH)

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Dokudovskaya S, Rout MP.SourceCNRS UMR 8126; Universite Paris-Sud 11; Institut Gustave Roussy; Villejuif, France.
Autophagy.Autophagy.2011 Nov 1;7(11). [Epub ahead of print]
We now seem to live in a small world, in which everyone is highly interconnected. Cells, too, often also display tremendous interconnectivities in their component systems. As a recent case in point, we have identified a conserved protein complex-the SEA complex-that links the nuclear pore complex (N
PMID 21804352

The role of Tecpr1 in selective autophagy as a cargo receptor.

Ogawa M, Sasakawa C.SourceDivision of Bacterial Infection; Institute of Medical Science; The University of Tokyo; Minato-ku, Tokyo Japan.
Autophagy.Autophagy.2011 Nov 1;7(11). [Epub ahead of print]
Bacterial intrusion of host cells can be recognized by the innate immune system, including autophagy, via multiple cellular pathways. We have identified Tecpr1 as an Atg5-binding partner, and found that Tecpr1 interacts with the Atg12-Atg5-Atg16L1 complex via binding to Atg5. In Shigella infected ce
PMID 21795850

Japanese Journal

Myelin basic protein as a novel genetic risk factor in rheumatoid arthritis-a genome-wide study combined with immunological analyses.

Terao Chikashi,Ohmura Koichiro,Katayama Masaki,Takahashi Meiko,Kokubo Miki,Diop Gora,Toda Yoshinobu,Yamamoto Natsuki,Human Disease Genomics Working Group,Rheumatoid Arthritis (RA) Clinical and Genetic Study Consortium,Shinkura Reiko,Shimizu Masakazu,Gut Ivo,Heath Simon,Melchers Inga,Manabe Toshiaki,Lathrop Mark,Mimori Tsuneyo,Yamada Ryo,Matsuda Fumihiko
PloS one 6(6), 2011-06
… Rheumatoid arthritis (RA) is a major cause of adult chronic inflammatory arthritis and a typical complex trait. … A novel risk variant, rs2000811, in intron2 of the myelin basic protein (MBP) at chromosome 18q23 showed strong association with RA (p = 2.7×10(-8), OR 1.23, 95% CI: 1.14-1.32). …
NAID 120003184064

Viral cell-to-cell movement requires formation of cortical punctate structures containing Red clover necrotic mosaic virus movement protein.

Kaido Masanori,Funatsu Naoko,Tsuno Yasuko,Mise Kazuyuki,Okuno Tetsuro
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… Movement protein (MP) of Red clover necrotic mosaic virus (RCNMV) forms punctate structures on the cortical endoplasmic reticulum (ER) of Nicotiana benthamiana cells, which are associated with viral RNA1 replication (Kaido et al., Virology 395, 232-242. … We investigated the significance of ER-targeting by MP during virus movement from cell to cell, by analyzing the function of a series of MPs with varying length deletions at their C-terminus, either fused or not fused with green fluorescent protein (GFP). …
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★リンクテーブル★

リンク元	「タンパク複合体」「タンパク質複合体」
拡張検索	「adaptor protein complex subunit」「nuclear cap-binding protein complex」「adaptor protein complex 3」
関連記事	「complex」「complexed」「complexes」