Heavy chain

Heavy chain

A heavy chain is the large polypeptide subunit of a protein complex, such as a motor protein (e.g. myosin, kinesin, or dynein) or antibody (or immunoglobulin). A typical antibody is composed of two immunoglobulin (Ig) heavy chains and two Ig light chains. Several different types of heavy chain exist that define the class or isotype of an antibody. These heavy chain types vary between different animals. All heavy chains contain a series of immunoglobulin domains, usually with one variable (IgV) domain that is important for binding antigen and several constant (IgC) domains.

In mammals

Classes

There are five types of mammalian immunoglobulin heavy chain: γ, δ, α, μ and ε.cite book | author = Janeway CA, Jr. "et al" | title = Immunobiology. | edition = 5th ed. | publisher = Garland Publishing | year = 2001 | id = [http://www.ncbi.nlm.nih.gov/books/bv.fcgi?call=bv.View..ShowTOC&rid=imm.TOC&depth=10 (electronic full text via NCBI Bookshelf)] ISBN 0-8153-3642-X ] They define "classes" of immunoglobulins.
* Heavy chains α and γ have approximately 450 amino acids.
* Heavy chains μ and ε have approximately 550 amino acids.

Regions

Each heavy chain has two regions:
* a "constant region" (which is the same for all immunoglobulins of the same class but differs between each class of immunoglobulins).
** Heavy chains γ, α and δ have a constant region composed of three tandem (in a line next to each other) immunoglobulin domains but also have a hinge region for added flexibility.cite journal |author=Woof J, Burton D |title=Human antibody-Fc receptor interactions illuminated by crystal structures |journal=Nat Rev Immunol |volume=4 |issue=2 |pages=89–99 |year=2004 |pmid=15040582 |doi=10.1038/nri1266]
** Heavy chains μ and ε have a constant region composed of four immunoglobulin domains.
* a "variable region" that differs between different B cells, but is the same for all immunoglobulins produced by the same B cell or B cell clone. The variable domain of any heavy chain is composed of a single immunoglobulin domain. These domains are about 110 amino acids long.

In fish

Jawed fish appear to be the most primitive animals that are able to make antibodies like those described for mammals. [ [http://www.medicine.uiowa.edu/cigw/fish.htm Fish heavy chain and light chain genes] ] However, fish do not have the same repertoire of antibodies that mammals possess. [Eva Bengtén, L. William Clem, Norman W. Miller, Gregory W. Warr and Melanie Wilson. "Channel catfish immunoglobulins: Repertoire and expression". Developmental & Comparative Immunology, Volume 30, Issues 1-2, Antibody repertoire development, 2006, Pages 77-92.] Three distinct Ig heavy chains have so far been identified in bony fish.

* The first identified was the μ (or "mu") heavy chain that is present in all jawed fish and is the heavy chain for what is thought to be the primordial immunoglobulin. The resulting antibody, IgM, is secreted as a tetramer (containing four polypeptide chains) in teleost fish instead of the typical pentamer (containing five polypeptide chains) found in mammals and sharks.

* The heavy chain (δ) for IgD was identified initially from the channel catfish and Atlantic salmon and is now well documented for many teleost fish. [Stein Tore Solem and Jørgen Stenvik. "Antibody repertoire development in teleosts--a review with emphasis on salmonids and Gadus morhua L". Developmental & Comparative Immunology, Volume 30, Issues 1-2, Antibody repertoire development, 2006, Pages 57-76.]

* The third teleost Ig heavy chain gene was identified very recently and does not resemble any of the heavy chains so far described for mammals. This heavy chain, identified in both rainbow trout (τ) [J.D. Hansen, E.D. Landis and R.B. Phillips. "Discovery of a unique Ig heavy-chain isotype (IgT) in rainbow trout: Implications for a distinctive B cell developmental pathway in teleost fish." Proceedings of the National Academy of Sciences U S A. Volume 102, Issue 19, 2005, pages 6919-24.] and zebrafish (ζ), [ N. Danilova, J. Bussmann, K. Jekosch, L.A Steiner. "The immunoglobulin heavy-chain locus in zebrafish: identification and expression of a previously unknown isotype, immunoglobulin Z." Nature Immunology, Volume 6, Issue 3, 2005, pages 295-302. ] could potentially form a distinct antibody isotype (IgT or IgZ) that may precede IgM in evolutionary terms.

Similar to the situation observed for bony fish, three distinct Ig heavy chain isotypes have been identified in cartilaginous fish. With the exception of IgM, these Ig heavy chain isotypes appear to be unique to cartilaginous fish and are designated IgM, IgW (also called IgX or IgNARC) and IgNAR. [H. Dooley and M.F. Flajnik. "Antibody repertoire development in cartilaginous fish". Developmental & Comparative Immunology, Volume 30, Issues 1-2, Antibody repertoire development, 2006, Pages 43-56.]

ee also

* Heavy chain disease

References

External links

*


Wikimedia Foundation. 2010.

Игры ⚽ Поможем написать реферат

Look at other dictionaries:

  • heavy chain — hev ē chān n either of the two larger of the four polypeptide chains comprising antibodies compare LIGHT CHAIN …   Medical dictionary

  • heavy chain — In general, the larger polypeptide in a multimeric protein. Thus the immunoglobulin heavy chain is of 50 kD, the light chain of 22 kD, whereas in myosin the heavy chain is very much larger (220 kD) than the light chains (heavy chain20 kD) …   Dictionary of molecular biology

  • heavy chain disease — heavy chain disease. См. болезнь тяжелых цепей. (Источник: «Англо русский толковый словарь генетических терминов». Арефьев В.А., Лисовенко Л.А., Москва: Изд во ВНИРО, 1995 г.) …   Молекулярная биология и генетика. Толковый словарь.

  • heavy chain disease — heavy chain disease. = Franklin syndrome (см.). (Источник: «Англо русский толковый словарь генетических терминов». Арефьев В.А., Лисовенко Л.А., Москва: Изд во ВНИРО, 1995 г.) …   Молекулярная биология и генетика. Толковый словарь.

  • Heavy chain disease — Infobox Disease Name = PAGENAME Caption = DiseasesDB = 442 DiseasesDB mult = DiseasesDB2|32226 | ICD10 = ICD10|C|88|1|c|81 ICD10|C|88|2|c|81 ICD9 = ICD9|273.2 ICDO = OMIM = MedlinePlus = eMedicineSubj = med eMedicineTopic = 958 eMedicine mult =… …   Wikipedia

  • heavy chain diseases — a group of rare malignant neoplasms of lymphoplasmacytic cells that secrete an M component consisting of monoclonal immunoglobulin heavy chains or heavy chain fragments; they are classified according to heavy chain type. See also alpha chain d.,… …   Medical dictionary

  • heavy chain — noun Date: 1964 either of the two larger of the four polypeptide chains comprising antibodies compare light chain …   New Collegiate Dictionary

  • heavy chain — Immunol. either of an identical pair of Y shaped polypeptides that, together with the light chains, constitute the antibody molecule. Also called H chain [1960 65] * * * …   Universalium

  • heavy chain — noun : either of the two larger of the four polypeptide chains that comprise antibodies compare light chain herein …   Useful english dictionary

  • Myosin-heavy-chain kinase — Identifiers EC number 2.7.11.7 CAS number 64763 54 8 …   Wikipedia

Share the article and excerpts

Direct link
… Do a right-click on the link above
and select “Copy Link”