Biology:Cytoglobin

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Cytoglobin is the protein product of CYGB, a human and mammalian gene.[1]

Cytoglobin is a globin molecule ubiquitously expressed in all tissues and most notably utilized in marine mammals. It was discovered in 2001[2] in hepatic stellate cells during liver fibrosis. Thus, it was originally called "stellate cell activated protein" or STAP.[3] It received its current name in 2002.[4] It is thought to help in the distribution and storage of oxygen as well as protect against hypoxia by scavenging reactive oxygen species . The predicted function of cytoglobin is the facilitation of oxygen among tissues that don't express myoglobin.[5]

Function

Cytoglobin is a ubiquitously expressed hexacoordinate hemoglobin that may facilitate diffusion of oxygen through tissues, scavenge nitric oxide or reactive oxygen species, or serve a protective function during oxidative stress.[1][6]

Structure

Cytoglobin has 30-40% sequence homology with myoglobin, and has a similar oxygen binding affinity. One of the major differences is the presence of a 20 amino acids extension at both the n and c terminus.[7]

Cytoglobin is a hexacoordinate heme protein. The heme iron in coordinated with histidine residues on both sides, HisF8 and HisE7. The HisE7 is considered to be an "endogenous ligand." In order for oxygen or another gaseous ligand to bind, the HisE7 must dissociate from the iron, making the binding kinetics relatively slow.[8]

Diagram of how the heme group in cytoglobin interacts with the surrounding amino acids of the globin protein. Normally, the iron is coordinated with histidine residues on both sides. The HisE7 must be dissociated in order for oxygen to bind.

In an oxidizing environment, a disulfide bond between Cys38 and Cys83 of the protein forms and causes a conformational change to move HisE7 out of the way, allowing oxygen to bind. Thus, oxygen binding is dependent on the redox state of the tissue.[7]

Applications

CYGB expression can be used as a specific marker with which hepatic stellate cells can be distinguished from portal myofibroblasts in the damaged human liver.[9]

References

  1. ↑ 1.0 1.1 "Entrez Gene: CYGB cytoglobin". https://www.ncbi.nlm.nih.gov/gene?Db=gene&Cmd=ShowDetailView&TermToSearch=114757. 
  2. ↑ "Characterization of a stellate cell activation-associated protein (STAP) with peroxidase activity found in rat hepatic stellate cells". The Journal of Biological Chemistry 276 (27): 25318–23. Jul 2001. doi:10.1074/jbc.M102630200. PMID 11320098. 
  3. ↑ Pesce, Alessandra; Bolognesi, Martino; Bocedi, Alessio; Ascenzi, Paolo; Dewilde, Sylvia; Moens, Luc; Hankeln, Thomas; Burmester, Thorsten (December 2002). "Neuroglobin and cytoglobin: Fresh blood for the vertebrate globin family" (in en). EMBO Reports 3 (12): 1146–1151. doi:10.1093/embo-reports/kvf248. ISSN 1469-221X. PMID 12475928. PMC 1308314. https://www.embopress.org/doi/10.1093/embo-reports/kvf248. 
  4. ↑ "Cytoglobin: a novel globin type ubiquitously expressed in vertebrate tissues". Molecular Biology and Evolution 19 (4): 416–21. Apr 2002. doi:10.1093/oxfordjournals.molbev.a004096. PMID 11919282. 
  5. ↑ "Why Diving Marine Mammals Resist Brain Damage from Low Oxygen". ScienceDaily. 20 December 2007. https://www.sciencedaily.com/releases/2007/12/071218192033.htm. 
  6. ↑ "A ubiquitously expressed human hexacoordinate hemoglobin". The Journal of Biological Chemistry 277 (22): 19538–45. May 2002. doi:10.1074/jbc.M201934200. PMID 11893755. 
  7. ↑ 7.0 7.1 Keller, T. C. Stevenson; Lechauve, Christophe; Keller, Alexander S.; Brooks, Steven; Weiss, Mitchell J.; Columbus, Linda; Ackerman, Hans; Cortese-Krott, Miriam M. et al. (2022-04-01). "The role of globins in cardiovascular physiology" (in en). Physiological Reviews 102 (2): 859–892. doi:10.1152/physrev.00037.2020. ISSN 0031-9333. PMID 34486392. 
  8. ↑ Hankeln, Thomas; Ebner, Bettina; Fuchs, Christine; Gerlach, Frank; Haberkamp, Mark; Laufs, Tilmann L.; Roesner, Anja; Schmidt, Marc et al. (2005-01-01). "Neuroglobin and cytoglobin in search of their role in the vertebrate globin family". Journal of Inorganic Biochemistry. Heme-diatomic interactions, Part 1 99 (1): 110–119. doi:10.1016/j.jinorgbio.2004.11.009. ISSN 0162-0134. PMID 15598495. https://www.sciencedirect.com/science/article/abs/pii/S0162013404003514. 
  9. ↑ "Cytoglobin is expressed in hepatic stellate cells, but not in myofibroblasts, in normal and fibrotic human liver". Laboratory Investigation 94 (2): 192–207. Feb 2014. doi:10.1038/labinvest.2013.135. PMID 24296877. 

Further reading



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