WordNet

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"
the 1st letter of the Roman alphabet (同)a
the blood group whose red cells carry the A antigen (同)type_A, group A

PrepTutorEJDIC

蛋白(たんばく)質
answer / ampere
arsenicの化学記号

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2012/04/09 23:27:57」(JST)

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Protein A is a 56 kDa MSCRAMM surface protein originally found in the cell wall of the bacterium Staphylococcus aureus. It is encoded by the spa gene and its regulation is controlled by DNA topology, cellular osmolarity, and a two-component system called ArlS-ArlR. It has found use in biochemical research because of its ability to bind immunoglobulins. It is composed of five homologous Ig-binding domains that fold into a three-helix bundle. Each domain is able to bind proteins from many of mammalian species, most notably IgGs. It binds the heavy chain with the Fc region of most immunoglobulins and also within the Fab region in the case of the human VH3 family. Through these interactions in serum, where IgG molecules are bound in the wrong orientation (in relation to normal antibody function), the bacteria disrupts opsonization and phagocytosis.

Protein A antibody binding

Protein A binds with high affinity to human IgG1 and IgG2 as well as mouse IgG2a and IgG2b. Protein A binds with moderate affinity to human IgM, IgA and IgE as well as to mouse IgG3 and IgG1.^[3] It does not react with human IgG3 or IgD, nor will it react to mouse IgM, IgA or IgE.

The capacity of protein A to bind antibodies with such high affinity is the driving motivation for its industrial scale use in biologic pharmaceuticals. The protein A used for production of antibodies in bio-pharmaceuticals is most commonly bound to a stationary phase chromatography resin.

Other antibody binding proteins

In addition to Protein A, other immunoglobulin-binding bacterial proteins such as Protein G, Protein A/G and Protein L are all commonly used to purify, immobilize or detect immunoglobulins.

Role in pathogenesis

As a pathogen Staphylococcus aureus utilizes Protein A, along with a host of other proteins and surface factors to aid its survival and, thus, virulence. Protein A helps inhibit phagocytic engulfment and acts as an immunological disguise. Mutants of S. aureus lacking protein A are more efficiently phagocytosed in vitro, and mutants in infection models have diminished virulence. ^[4]

Research

Recombinant Staphylococcal Protein A is often produced in E. coli for use in immunology and other biological research. One recombinant form of Protein A is called MabSelect^[5]. Protein A is often coupled to other molecules such as a fluorescent dye, enzymes, biotin, colloidal gold or radioactive iodine without affecting the antibody binding site. It is also widely utilized coupled to magnetic, latex and agarose beads.

Protein A is often immobilized onto a solid support and used as reliable method for purifying total IgG from crude protein mixtures such as serum or ascites fluid, or coupled with one of the above markers to detect the presence of antibodies. Immunoprecipitation studies with protein A conjugated to beads are also commonly used to purify proteins or protein complexes indirectly through antibodies against the protein or protein complex of interest.

References

^ Graille M, Stura EA, Corper AL, Sutton BJ, Taussig MJ, Charbonnier JB, Silverman GJ. (May 2000). "Crystal structure of a Staphylococcus aureus protein A domain complexed with the Fab fragment of a human IgM antibody: structural basis for recognition of B-cell receptors and superantigen activity.". Proc Natl Acad Sci U S A. 97 (10): 5399–404. PMC 25840. PMID 10805799. http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=25840.
^ Idusogie EE, Presta LG, Gazzano-Santoro H, Totpal K, Wong PY, Ultsch M, Meng YG, Mulkerrin MG. (April 2000). "Mapping of the C1q binding site on rituxan, a chimeric antibody with a human IgG1 Fc.". J Immunol. 164 (8): 4178–84. PMID 10754313.
^ http://www.gelifesciences.com/aptrix/upp00919.nsf/Content/B7A1BAD977A2AF13C1257628001D1ECD/$file/11003558AA.pdf
^ Goodyear CS and Silverman GJ. Death by a B-cell superantigen: In vivo VH targeted apoptotic supra-clonal B-cell deletion by a staphylococcal toxin. J. Exp. Med. 2003 197: 1125-1139.
^ http://www.gelifesciences.com/aptrix/upp00919.nsf/Content/17D93C2E6A580E57C1257628001CE677/$file/18114994AE.pdf

UpToDate Contents

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English Journal

Investigation of antibacterial mechanism and identification of bacterial protein targets mediated by antibacterial medicinal plant extracts.

Yong AL1, Ooh KF1, Ong HC2, Chai TT3, Wong FC4.
Food chemistry.Food Chem.2015 Nov 1;186:32-6. doi: 10.1016/j.foodchem.2014.11.103. Epub 2014 Nov 26.
In this paper, we investigated the antibacterial mechanism and potential therapeutic targets of three antibacterial medicinal plants. Upon treatment with the plant extracts, bacterial proteins were extracted and resolved using denaturing gel electrophoresis. Differentially-expressed bacterial protei
PMID 25976788

A novel dynamic flow immunochromatographic test (DFICT) using gold nanoparticles for the serological detection of Toxoplasma gondii infection in dogs and cats.

Jiang W1, Liu Y2, Chen Y2, Yang Q3, Chun P3, Yao K3, Han X2, Wang S2, Yu S2, Liu Y4, Wang Q5.
Biosensors & bioelectronics.Biosens Bioelectron.2015 Oct 15;72:133-9. doi: 10.1016/j.bios.2015.04.035. Epub 2015 Apr 16.
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PMID 25978441

Expression, purification and characterization of cold shock protein A of Corynebacterium pseudotuberculosis.

Lindae A1, Eberle RJ1, Caruso IP1, Coronado MA1, de Moraes FR1, Azevedo V2, Arni RK3.
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The gram-positive bacterium Corynebacterium pseudotuberculosis is the causative agent of different diseases that cause dramatically reduced yields of wool and milk, and results in weight loss, carcass condemnation and also death mainly in sheep, equids, cattle and goats and therefore globally result
PMID 25907380

Japanese Journal

Two-step hydrolysis of rice (Oryza sativa) husk as treated by semi-flow hot-compressed water

Phaiboonsilpa Natthanon,Ogura Mai,Yamauchi Kazuchika,Rabemanolontsoa Harifara,Saka Shiro
Industrial Crops and Products 49, 484-491, 2013-08-00
… In addition, protein was found to some extent to be hydrolyzed by the hot-compressed water treatment and various amino acids to form the protein of rice husk were identified. … Some additional decomposition of lignin and protein was revealed at this stage as well. …
NAID 120005302076

Comprehensive microRNA Analysis Identifies miR-24 and miR-125a-5p as Plasma Biomarkers for Rheumatoid Arthritis.

Murata Koichi,Furu Moritoshi,Yoshitomi Hiroyuki,Ishikawa Masahiro,Shibuya Hideyuki,Hashimoto Motomu,Imura Yoshitaka,Fujii Takao,Ito Hiromu,Mimori Tsuneyo,Matsuda Shuichi
PloS one 8(7), 2013-07-18
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NAID 120005304021

タンデム質量分析ソフトウェアCoCoozoのマルチコアCPUとGPUを用いた高速化

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NAID 110009586919

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★リンクテーブル★

リンク元	「staphylococcal protein A」
拡張検索	「cyclic AMP response element-binding protein A」「apolipoprotein A-I」「apolipoprotein A2」「proto-oncogene protein A-Raf」
関連記事	「A」「Ad」

「staphylococcal protein A」

Protein A
	Structure of a domain of protein A as a three-helix bundle binding to the heavy variable chain of a VH3 human Fab left. Minimized protein A bound to Fc fragment of Rituximab.
Identifiers
Symbol	SpA
SCOP	1DEE
SUPERFAMILY	1DEE