Hemolysin

Hemolysin

Pfam_box
Symbol = Leukocidin
Name =


width =250
caption =Alpha-hemolysin, a transmembrane heptamer
Pfam= PF07968
InterPro= IPR001340
SMART=
Prosite =
SCOP =
TCDB =
OPM family= 35
OPM protein= 7ahl
PDB=PDB3|1t5rH:57-303 PDB3|1lkfA:60-310 PDB3|2lkfA:60-310PDB3|3lkfA:60-310 PDB3|1pvl :58-308 PDB3|7ahlG:62-314

Hemolysins are exotoxin protein produced by bacteria which causes lysis of red blood cells "in vitro". Visualization of hemolysis of red blood cells in agar plates facilitates the categorization of some pathogenic bacteria such as "Streptococcus". Although the lytic activity of some hemolysins on red blood cells may be important for nutrient acquisition or for causing certain conditions such as anemia, many hemolysin-producing pathogens do not cause significant lysis of red blood cells during infection. Although hemolysins are able to lyse red blood cells "in vitro", the ability of hemolysins to target other cells, including white blood cells, often accounts for the effects of hemolysins in the host.

Purpose of hemolysin

Bacteria may use hemolysins as a way to obtain nutrients from host cells. For example, iron may be a limiting factor in the growth of various pathogenic bacteria. [Sritharan M. Iron and bacterial virulence. Indian J Med Microbiol [serial online] 2006 [cited 2007 Jun 17] ;24:163-164. Available from: [http://www.ijmm.org/text.asp?2006/24/3/163/26987] ] Since free iron may generate damaging free radicals, free iron is typically maintained at low concentrations within the body. Red blood cells are rich in iron-containing heme. Lysis of these cells releases heme into the surroundings, allowing the bacteria to take up the free iron.

The regulation of gene expression of hemolysins (such as streptolysin S) is a system repressed in the presence of iron. [cite journal |author=Griffiths BB, McClain O |title=The role of iron in the growth and hemolysin (Streptolysin S) production in Streptococcus pyogenes |journal=J. Basic Microbiol. |volume=28 |issue=7 |pages=427–36 |year=1988 |pmid=3065477 |doi=] This ensures that hemolysin is produced only when needed.

Some hemolysins, such as listeriolysin O, allow bacteria to evade the immune system by escaping from phagosomes. Hemolysins may also mediate bacterial escape from host cells.

It is now believed that many clinically relevant fungi also produce hemolysins. [Vesper SJ, Vesper MJ. Adv Appl Microbiol. 2004;55:191-213]

3D structure of hemolysin

Hemolysin forms a heptameric beta-barrel in biological membranes. [ Structure of staphylococcal alpha-hemolysin, a heptameric transmembrane pore. Song L, Hobaugh MR, Shustak C, Cheley S, Bayley H, Gouaux JE; "Science" 1996;274:1859-1866. PMID|8943190]

References

ee also

* Hemolysis (microbiology)
* Pore forming toxins

External links

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Look at other dictionaries:

  • hemolysin — [hē′mō lī΄sin, hem′ōlī′sin; hē mäl′ə sin] n. [< HEMO + Gr lysis, a dissolving + IN1] a substance formed in the blood, as by bacterial action, that causes the destruction of red corpuscles with liberation of hemoglobin …   English World dictionary

  • hemolysin — noun Etymology: International Scientific Vocabulary Date: 1900 a substance that causes the dissolution of red blood cells …   New Collegiate Dictionary

  • hemolysin — (he mol ī sin) A substance that causes hemolysis (the lysis of red blood cells). At least some hemolysins are enzymes that destroy the phospholipids in erythrocyte plasma membranes …   Dictionary of microbiology

  • hemolysin — /hi mol i sin, hee meuh luy , hem euh /, n. Immunol. a substance, as an antibody, that in cooperation with complement causes dissolution of red blood cells. [1895 1900; HEMO + LYSIN] * * * …   Universalium

  • hemolysin — noun Any substance (often an exotoxin) that damages the membranes of red blood cells and thus releases hemoglobin See Also: hemolysis, hemolytic …   Wiktionary

  • hemolysin — 1. Any substance elaborated by a living agent and capable of causing lysis of red blood cells and liberation of their hemoglobin. SYN: erythrocytolysin, erythrolysin. 2. A sensitizing (complement fixing) antibody that combines with red blood… …   Medical dictionary

  • hemolysin — n. substance which causes the dissolution of red blood cells …   English contemporary dictionary

  • hemolysin — he·mo·ly·sin …   English syllables

  • hemolysin — he•mol•y•sin [[t]hɪˈmɒl ɪ sɪn[/t]] n. imu any substance in the blood that initiates the dissolution of red blood cells, as a bacterial toxin • Etymology: 1895–1900 …   From formal English to slang

  • hemolysin — noun any substance that can cause lysis (destruction) of erythrocytes (red blood cells) and the release of their hemoglobin • Syn: ↑haemolysin, ↑erythrolysin, ↑erythrocytolysin • Hypernyms: ↑organic compound • Hyponyms: ↑ …   Useful english dictionary

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