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Resolved errors in CALB2 and calbindin-D9k as S100G
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{{protein
{{Confusing|date=December 2006}}
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{{protein
| Name = calbindin 1, 28kDa
| Name = calbindin 1, 28kDa
| caption = NMR solution structure of Ca<sup>2+</sup>-loaded calbindin D28K.<ref name="pmid16799559">{{PDB|2G9B}}; {{cite journal | author = Kojetin DJ, Venters RA, Kordys DR, Thompson RJ, Kumar R, Cavanagh J | title = Structure, binding interface and hydrophobic transitions of Ca2+-loaded calbindin-D(28K) | journal = Nat. Struct. Mol. Biol. | volume = 13 | issue = 7 | pages = 641–7 | year = 2006 | month = July | pmid = 16799559 | doi = 10.1038/nsmb1112 | url = | issn = }}</ref>
| caption = NMR solution structure of Ca<sup>2+</sup>-loaded calbindin D28K.<ref name="pmid16799559">{{PDB|2G9B}}; {{cite journal | author = Kojetin DJ, Venters RA, Kordys DR, Thompson RJ, Kumar R, Cavanagh J | title = Structure, binding interface and hydrophobic transitions of Ca2+-loaded calbindin-D(28K) | journal = Nat. Struct. Mol. Biol. | volume = 13 | issue = 7 | pages = 641–7 | year = 2006 | pmid = 16799559 | doi = 10.1038/nsmb1112 | url = | issn = }}</ref>
| image = Calbindin2G9B.pdb.png
| image = Calbindin2G9B.pdb.png
| width =
| width =
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| LocusSupplementaryData =
| LocusSupplementaryData =
}}
}}
'''Calbindin''' is a [[calcium in biology|calcium]]-binding protein belonging to the [[troponin C]] superfamily. It was originally described as a 27-kD protein induced by [[vitamin D]] in the duodenum of the chick. In the brain, its synthesis is independent of vitamin-D-derived hormones. Calbindin contains 4 active calcium-binding [[protein domain|domain]]s, and 2 modified domains that presumably have lost their calcium-binding capacity.
'''Calbindin''' refers to several [[calcium in biology|calcium]]-binding protein belonging to the [[troponin C]] superfamily. They were originally described as [[vitamin D-dependent calcium-binding protein]]s in the intestine and kidney in the chick and mammals.


==Calbindin-D9k==
==Calbindin-D28k==
'''Calbindin-D28k''' was fist shown to be present in the intestine in birds and then found in the mammalian kidney. It is also expressed in a number of [[neuroendocrine]] cells, particularly in the [[cerebellum]]. It is encoded in humans by the ''CALB1'' gene.
'''Calbindin-D9k''' is present in [[mammal]]ian intestinal [[epithelial cell]]s (enterocytes) and mediates the transport of calcium across the enterocytes from the apical side, where entry is regulated by the [[calcium channel]] [[TRPV6]], to the basolateral side, where [[calcium pump]]s such as [[Plasma membrane Ca2+ ATPase|PMCA]]1 utilize intracellular [[adenosine triphosphate]] to pump calcium into the blood. Calbindin-D9k can also be found in the kidney and [[uterus]] in some mammalian species.


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Calbindin-D28k contains 4 active calcium-binding [[protein domain|domain]]s, and 2 modified domains that have lost their calcium-binding capacity. Calbindin-D28k acts as a calcium buffer and calcium sensor and can hold four Ca<sup>2+</sup> in the [[EF-hands]] of loops EF1, EF3, EF4 and EF5. The structure was solved using high-resolution NMR and which was one of the largest proteins then to be determined <ref name="pmid16799559"></ref>. The sequence of Calbindin is 263 residues in length and has only one chain. The sequence consists mostly of alpha helicies but beta sheets are not absent. According to the PDB it is 44% helical with 14 helices containing 117 residues, and 4% beta sheet with 9 strands containing 13 residues.
The transport of calcium across the enterocyte cytoplasm appears to be [[rate-limiting reaction|rate-limiting]] for calcium absorption in the intestine; the presence of calbindin increases the amount of calcium crossing the cell without raising the free concentration. Calbindin-D9k may also stimulate the basolateral calcium-pumping [[ATPase]]s. [[gene expression|Expression]] of calbindin-D9k and calbindin-D28k are both stimulated by the active vitamin D [[metabolite]], [[calcitriol]] although the precise mechanisms are still controversial. In mice in which the [[biochemical receptor|receptor]] for vitamin D is not [[gene expression|expressed]], calbindin-D9k is reduced, but not absent.


Calbindin-D28k is a [[vitamin D]] responsive gene in many tissues, in particular the chick intestine, where it has a clear function in mediating calcium absorption.<ref>{{cite journal|last=Wasserman|first=RH|coauthors=Fullmer, CS|title=On the molecular mechanism of intestinal calcium transport.|journal=Advances in experimental medicine and biology|date=1989|volume=249|pages=45-65|pmid=2543194}}</ref> In the brain, its synthesis is independent of vitamin-D.
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==Calbindin-D28k==

'''Calbindin-D28k''' performs a similar role in the intestine in birds and in the mammalian kidney; it is also found in a number of other [[neuroendocrine]] cells, particularly in the [[cerebellum]]. There is no [[homology (biology)|homology]] between calbindin-D28k and calbindin-D9k, apart from their calcium binding domains ([[EF-hands]]): calbindin-D9k has two EF-hands, and calbindin-D28k has six.
There is no [[homology (biology)|homology]] between calbindin-D28k and calbindin-D9k, apart from their calcium binding domains ([[EF-hands]]): calbindin-D9k has two EF-hands, and calbindin-D28k has six.

==Calretinin==
{{Main article|Calretinin}}
'''Calretinin''' is a 29kDa protein with 58% homology to calbindin-28k and principally found in nervous tissues.<ref>{{cite journal|last=Rogers|first=JH|title=Calretinin: a gene for a novel calcium-binding protein expressed principally in neurons.|journal=The Journal of cell biology|date=1987|volume=105|issue=3|pages=1343-53|pmid=3654755}}</ref> It is encoded in humans by the ''CALB2'' gene.

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==Calbindin-D9k==
{{See also|S100G}}
'''Calbindin-D9k''' is present in [[mammal]]ian intestinal [[epithelial cell]]s (enterocytes). Calbindin-D9k can also be found in the kidney and [[uterus]] in some mammalian species. It in encoded in humans by the ''[[S100G]]'' gene which has also been termed ''CALB3''.

Calbindin-D9k is a member of the [[S100]] family of [[calcium-binding proteins]]. It has two [[EF-hands]] sequences which bind Ca<sup>2+</sup> with high affinity.


Calbindin-D9k mediates the transport of calcium across the enterocytes from the apical side, where entry is regulated by the [[calcium channel]] [[TRPV6]], to the basolateral side, where [[calcium pump]]s such as [[Plasma membrane Ca2+ ATPase|PMCA]]1 utilize intracellular [[adenosine triphosphate]] to pump calcium into the blood <ref>{{cite journal|last=Wasserman|first=RH|coauthors=Chandler, JS, Meyer, SA, Smith, CA, Brindak, ME, Fullmer, CS, Penniston, JT, Kumar, R|title=Intestinal calcium transport and calcium extrusion processes at the basolateral membrane.|journal=The Journal of nutrition|date=1992|volume=122|pages=662-71|pmid=1311756}}</ref>. The transport of calcium across the enterocyte cytoplasm appears to be rate-limiting for calcium absorption in the intestine; the presence of calbindin increases the amount of calcium crossing the cell without raising the free concentration<ref>{{cite journal|last=Feher|first=JJ|coauthors=Fullmer, CS, Wasserman, RH|title=Role of facilitated diffusion of calcium by calbindin in intestinal calcium absorption.|journal=The American journal of physiology|date=1992|volume=262|issue=2 Pt 1|pages=C517-26|pmid=1539638}}</ref>. Calbindin-D9k may also stimulate the basolateral calcium-pumping [[ATPase]]s. [[gene expression|Expression]] of calbindin-D9k, like that of calbindin-D28k, is stimulated by the active vitamin D [[metabolite]], [[calcitriol]] although the precise mechanisms are still controversial<ref>{{cite journal|last=Barley|first=NF|coauthors=Prathalingam, SR, Zhi, P, Legon, S, Howard, A, Walters, JR|title=Factors involved in the duodenal expression of the human calbindin-D9k gene.|journal=The Biochemical journal|date=1999|volume=341|pages=491-500|pmid=10417310}}</ref>. In mice in which the [[biochemical receptor|receptor]] for vitamin D is not [[gene expression|expressed]], calbindin-D9k is reduced, but not absent.
⚫
Calbindin acts as a calcium buffer and calcium sensor and can hold four Ca2+ in loops EF1, EF3, EF4 and EF5. When Calbindin binds with Ca2+ it shows hydrophobic properties which are considered the first details into how this protein functions. The structure was solved using high-resolution NMR and is one of the largest proteins to be determined. The sequence of Calbindin is 263 residues in length and has only one chain. The sequence consists mostly of alpha helicies but beta sheets are not absent. According to the PDB it is 44% helical with 14 helices containing 117 residues, and 4% beta sheet with 9 strands containing 13 residues.


==See also==
==See also==
* [[Vitamin D-dependent calcium-binding protein]]
* [[Vitamin D-dependent calcium-binding protein]]
* [[Calretinin]]
* [[S100G]]


==References==
==References==
{{reflist}}
{{reflist}}
== Further reading ==
{{refbegin}}
* {{cite journal| author=Barley NF, Prathalingam SR, Zhi P, Legon S, Howard A, Walters JRF| title=Factors involved in the duodenal expression of the human calbindin-D9k gene| journal=Biochemical Journal| year=1999|volume=341|pages=491–500|pmid=10417310|url=http://www.biochemj.org/bj/341/0491/bj3410491.htm|accessdate=2007-10-10| doi=10.1042/0264-6021:3410491| pmc=1220384}}
{{refend}}


{{NLM content}}
{{NLM content}}

Revision as of 11:55, 10 April 2011

calbindin 1, 28kDa
NMR solution structure of Ca2+-loaded calbindin D28K.[1]
Identifiers
SymbolCALB1
Alt. symbolsCALB
NCBI gene793
HGNC1434
OMIM114050
RefSeqNM_004929
UniProtP05937
Other data
LocusChr. 8 p11
Search for
StructuresSwiss-model
DomainsInterPro
calbindin 2, 29kDa (calretinin)
Identifiers
SymbolCALB2
NCBI gene794
HGNC1435
OMIM114051
RefSeqNM_001740
UniProtP22676
Other data
LocusChr. 16 q22.1
Search for
StructuresSwiss-model
DomainsInterPro

Calbindin refers to several calcium-binding protein belonging to the troponin C superfamily. They were originally described as vitamin D-dependent calcium-binding proteins in the intestine and kidney in the chick and mammals.

Calbindin-D28k

Calbindin-D28k was fist shown to be present in the intestine in birds and then found in the mammalian kidney. It is also expressed in a number of neuroendocrine cells, particularly in the cerebellum. It is encoded in humans by the CALB1 gene.

Calbindin-D28k contains 4 active calcium-binding domains, and 2 modified domains that have lost their calcium-binding capacity. Calbindin-D28k acts as a calcium buffer and calcium sensor and can hold four Ca2+ in the EF-hands of loops EF1, EF3, EF4 and EF5. The structure was solved using high-resolution NMR and which was one of the largest proteins then to be determined [1]. The sequence of Calbindin is 263 residues in length and has only one chain. The sequence consists mostly of alpha helicies but beta sheets are not absent. According to the PDB it is 44% helical with 14 helices containing 117 residues, and 4% beta sheet with 9 strands containing 13 residues.

Calbindin-D28k is a vitamin D responsive gene in many tissues, in particular the chick intestine, where it has a clear function in mediating calcium absorption.[2] In the brain, its synthesis is independent of vitamin-D.

There is no homology between calbindin-D28k and calbindin-D9k, apart from their calcium binding domains (EF-hands): calbindin-D9k has two EF-hands, and calbindin-D28k has six.

Calretinin

Main article: Calretinin

Calretinin is a 29kDa protein with 58% homology to calbindin-28k and principally found in nervous tissues.[3] It is encoded in humans by the CALB2 gene.

Calbindin-D9k

See also: S100G

Calbindin-D9k is present in mammalian intestinal epithelial cells (enterocytes). Calbindin-D9k can also be found in the kidney and uterus in some mammalian species. It in encoded in humans by the S100G gene which has also been termed CALB3.

Calbindin-D9k is a member of the S100 family of calcium-binding proteins. It has two EF-hands sequences which bind Ca2+ with high affinity.

Calbindin-D9k mediates the transport of calcium across the enterocytes from the apical side, where entry is regulated by the calcium channel TRPV6, to the basolateral side, where calcium pumps such as PMCA1 utilize intracellular adenosine triphosphate to pump calcium into the blood [4]. The transport of calcium across the enterocyte cytoplasm appears to be rate-limiting for calcium absorption in the intestine; the presence of calbindin increases the amount of calcium crossing the cell without raising the free concentration[5]. Calbindin-D9k may also stimulate the basolateral calcium-pumping ATPases. Expression of calbindin-D9k, like that of calbindin-D28k, is stimulated by the active vitamin D metabolite, calcitriol although the precise mechanisms are still controversial[6]. In mice in which the receptor for vitamin D is not expressed, calbindin-D9k is reduced, but not absent.

See also

References

  1. ^ a b PDB: 2G9B​; Kojetin DJ, Venters RA, Kordys DR, Thompson RJ, Kumar R, Cavanagh J (2006). "Structure, binding interface and hydrophobic transitions of Ca2+-loaded calbindin-D(28K)". Nat. Struct. Mol. Biol. 13 (7): 641–7. doi:10.1038/nsmb1112. PMID 16799559.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  2. ^ Wasserman, RH (1989). "On the molecular mechanism of intestinal calcium transport". Advances in experimental medicine and biology. 249: 45–65. PMID 2543194. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  3. ^ Rogers, JH (1987). "Calretinin: a gene for a novel calcium-binding protein expressed principally in neurons". The Journal of cell biology. 105 (3): 1343–53. PMID 3654755.
  4. ^ Wasserman, RH (1992). "Intestinal calcium transport and calcium extrusion processes at the basolateral membrane". The Journal of nutrition. 122: 662–71. PMID 1311756. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  5. ^ Feher, JJ (1992). "Role of facilitated diffusion of calcium by calbindin in intestinal calcium absorption". The American journal of physiology. 262 (2 Pt 1): C517-26. PMID 1539638. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  6. ^ Barley, NF (1999). "Factors involved in the duodenal expression of the human calbindin-D9k gene". The Biochemical journal. 341: 491–500. PMID 10417310. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)

This article incorporates text from the United States National Library of Medicine, which is in the public domain.

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