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Intro and Protein structure
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{{Infobox_gene}}
{{Infobox_gene}}
'''Bestrophin-1''' is a [[protein]] that in humans is encoded by the ''BEST1'' [[gene]].<ref name="pmid1302019">{{cite journal | vauthors = Stone EM, Nichols BE, Streb LM, Kimura AE, Sheffield VC | title = Genetic linkage of vitelliform macular degeneration (Best's disease) to chromosome 11q13 | journal = Nature Genetics | volume = 1 | issue = 4 | pages = 246–50 | date = July 1992 | pmid = 1302019 | pmc = | doi = 10.1038/ng0792-246 }}</ref><ref name="pmid17003041">{{cite journal | vauthors = Barro Soria R, Spitzner M, Schreiber R, Kunzelmann K | title = Bestrophin 1 enables Ca<sup>2+</sup> activated Cl<sup>−</sup> conductance in epithelia | journal = The Journal of Biological Chemistry | volume = 284 | issue = 43 | pages = 29405–12 | date = October 2009 | pmid = 17003041 | pmc = 2785573 | doi = 10.1074/jbc.M605716200 }}</ref><ref name="entrez">{{cite web | title = Entrez Gene: BEST1 bestrophin 1| url = http://www.ncbi.nlm.nih.gov/sites/entrez?Db=gene&Cmd=ShowDetailView&TermToSearch=7439| accessdate = }}</ref>
'''Bestrophin-1''' is a [[protein]] that, in humans, is encoded by the ''BEST1'' [[gene]] (RPD ID - 5T5N/4RDQ).<ref name="pmid1302019">{{cite journal | vauthors = Stone EM, Nichols BE, Streb LM, Kimura AE, Sheffield VC | title = Genetic linkage of vitelliform macular degeneration (Best's disease) to chromosome 11q13 | journal = Nature Genetics | volume = 1 | issue = 4 | pages = 246–50 | date = July 1992 | pmid = 1302019 | pmc = | doi = 10.1038/ng0792-246 }}</ref><ref name="pmid17003041">{{cite journal | vauthors = Barro Soria R, Spitzner M, Schreiber R, Kunzelmann K | title = Bestrophin 1 enables Ca<sup>2+</sup> activated Cl<sup>−</sup> conductance in epithelia | journal = The Journal of Biological Chemistry | volume = 284 | issue = 43 | pages = 29405–12 | date = October 2009 | pmid = 17003041 | pmc = 2785573 | doi = 10.1074/jbc.M605716200 }}</ref><ref name="entrez">{{cite web | title = Entrez Gene: BEST1 bestrophin 1| url = http://www.ncbi.nlm.nih.gov/sites/entrez?Db=gene&Cmd=ShowDetailView&TermToSearch=7439| accessdate = }}</ref>
[[File:Bestrophin-1_5T5N_Xray_Cystallography.png|link=https://en.wikipedia.org/wiki/File:Bestrophin-1_5T5N_Xray_Cystallography.png|thumb|Calcium-activated chloride channel bestrophin-1 (BEST1), triple mutant: I76A, F80A, F84A; in complex with an Fab antibody fragment, chloride, and calcium. From RCSB PDB.]]
The bestrophin family is comprised of four ancestrally linked genes (BEST1, [[BEST2]], BEST3, and BEST4) that code for [[integral membrane proteins]].<ref name="Kunzelmann_20152">{{cite journal|date=September 2015|title=TMEM16, LRRC8A, bestrophin: chloride channels controlled by Ca(2+) and cell volume|journal=Trends in Biochemical Sciences|volume=40|issue=9|pages=535–43|doi=10.1016/j.tibs.2015.07.005|pmid=26254230|vauthors=Kunzelmann K}}</ref> The [[Bestrophin|bestrophins]] were first identified in humans by relating a BEST1 [[mutation]] with Best [[vitelliform macular dystrophy]] (BVMD).<ref name="Johnson_20172">{{cite journal|date=January 2017|title=Bestrophin 1 and retinal disease|journal=Progress in Retinal and Eye Research|doi=10.1016/j.preteyeres.2017.01.006|pmid=28153808|vauthors=Johnson AA, Guziewicz KE, Lee CJ, Kalathur RC, Pulido JS, Marmorstein LY, Marmorstein AD}}</ref> Mutations in the BEST1 gene have been determined as the primary cause for at least five different degenerative [[Retina|retinal]] diseases.<ref name="Johnson_20172" />


== Structure in humans ==
It can be associated with [[Vitelliform macular dystrophy]].


== Function ==
===Gene structure===


The bestrophin genes share a conserved gene structure, with almost identical sizes of the 8 RFP-TM domain-encoding exons and highly conserved exon-intron boundaries. Each of the 4 bestrophin genes has a unique 3-prime end of variable length.<ref name="entrez" /><ref name="pmid12032738">{{cite journal | vauthors = Stöhr H, Marquardt A, Nanda I, Schmid M, Weber BH | title = Three novel human VMD2-like genes are members of the evolutionary highly conserved RFP-TM family | journal = European Journal of Human Genetics | volume = 10 | issue = 4 | pages = 281–4 | date = April 2002 | pmid = 12032738 | doi = 10.1038/sj.ejhg.5200796 }}</ref><ref name="pmid12907679">{{cite journal | vauthors = Tsunenari T, Sun H, Williams J, Cahill H, Smallwood P, Yau KW, Nathans J | title = Structure-function analysis of the bestrophin family of anion channels | journal = The Journal of Biological Chemistry | volume = 278 | issue = 42 | pages = 41114–25 | date = October 2003 | pmid = 12907679 | pmc = 2885917 | doi = 10.1074/jbc.M306150200 }}</ref>
BEST1 belongs to the bestrophin family of calcium-activated anion channels, which includes [[BEST2]], BEST3, and BEST4. Bestrophins are transmembrane (TM) proteins that share a homology region containing a high content of aromatic residues, including an invariant arg-phe-pro (RFP) motif. Bestrophins are believed to function as [[chloride channel]]s that may also serve as regulators of intracellular calcium signalling.<ref name="pmid18391176">{{cite journal | vauthors = Hartzell HC, Qu Z, Yu K, Xiao Q, Chien LT | title = Molecular physiology of bestrophins: multifunctional membrane proteins linked to best disease and other retinopathies | journal = Physiological Reviews | volume = 88 | issue = 2 | pages = 639–72 | date = April 2008 | pmid = 18391176 | doi = 10.1152/physrev.00022.2007 }}</ref>


BEST1 has been shown by two independent studies to be regulated by [[Microphthalmia-associated transcription factor]].<ref name="pmid17085443">{{cite journal | vauthors = Esumi N, Kachi S, Campochiaro PA, Zack DJ | title = VMD2 promoter requires two proximal E-box sites for its activity in vivo and is regulated by the MITF-TFE family | journal = The Journal of Biological Chemistry | volume = 282 | issue = 3 | pages = 1838–50 | date = January 2007 | pmid = 17085443 | doi = 10.1074/jbc.M609517200 }}</ref><ref name="pmidunknown">{{cite journal | vauthors = Hoek KS, Schlegel NC, Eichhoff OM, Widmer DS, Praetorius C, Einarsson SO, Valgeirsdottir S, Bergsteinsdottir K, Schepsky A, Dummer R, Steingrimsson E | title = Novel MITF targets identified using a two-step DNA microarray strategy | journal = Pigment Cell & Melanoma Research | volume = 21 | issue = 6 | pages = 665–76 | date = December 2008 | pmid = 19067971 | doi = 10.1111/j.1755-148X.2008.00505.x }}</ref>
==Gene structure==


=== Protein structure ===
The bestrophin genes share a conserved gene structure, with almost identical sizes of the 8 RFP-TM domain-encoding exons and highly conserved exon-intron boundaries. Each of the 4 bestrophin genes has a unique 3-prime end of variable length.<ref name="entrez"/><ref name="pmid12032738">{{cite journal | vauthors = Stöhr H, Marquardt A, Nanda I, Schmid M, Weber BH | title = Three novel human VMD2-like genes are members of the evolutionary highly conserved RFP-TM family | journal = European Journal of Human Genetics | volume = 10 | issue = 4 | pages = 281–4 | date = April 2002 | pmid = 12032738 | doi = 10.1038/sj.ejhg.5200796 }}</ref><ref name="pmid12907679">{{cite journal | vauthors = Tsunenari T, Sun H, Williams J, Cahill H, Smallwood P, Yau KW, Nathans J | title = Structure-function analysis of the bestrophin family of anion channels | journal = The Journal of Biological Chemistry | volume = 278 | issue = 42 | pages = 41114–25 | date = October 2003 | pmid = 12907679 | pmc = 2885917 | doi = 10.1074/jbc.M306150200 }}</ref>
Bestrophin 1 is an integral membrane protein found only in the [[retinal pigment epithelium]] (RPE) of the eye.<ref name="Strauss_2012">{{cite journal|year=2012|title=A potential cytosolic function of bestrophin-1|url=|journal=Advances in Experimental Medicine and Biology|volume=723|issue=|pages=603–10|doi=10.1007/978-1-4614-0631-0_77|pmid=22183384|vauthors=Strauss O, Neussert R, Müller C, Milenkovic VM}}</ref> Within the RPE layer, Best1 is primarily located on the [[Basolateral|basolateral plasma membrane]]. [[Protein crystallization]] structures indicate the primary ion channel function of Best1 as well as the calcium regulatory capabilities.<ref name="Strauss_2012" /><ref name="Johnson_2017">{{cite journal|date=January 2017|title=Bestrophin 1 and retinal disease|journal=Progress in Retinal and Eye Research|doi=10.1016/j.preteyeres.2017.01.006|pmid=28153808|vauthors=Johnson AA, Guziewicz KE, Lee CJ, Kalathur RC, Pulido JS, Marmorstein LY, Marmorstein AD}}</ref>Bestrophin 1 consists of 585 [[Amino acid|amino acids]] and both [[N-terminus|N-]] and the [[C-terminus|C-termini]] are located within the cell.
[[File:Bestrophin-1_Biolgical_Assembly_1.png|link=https://en.wikipedia.org/wiki/File:Bestrophin-1_Biolgical_Assembly_1.png|thumb|Calcium-activated chloride channel bestrophin-1 (BEST1), triple mutant: I76A, F80A, F84A; in complex with an Fab antibody fragment, chloride, and calcium. From RCSB PDB]]
The structure of Best1 consists of five identical subunits that each span the membrane four times and form a continuous, funnel-shaped pore via the second [[Transmembrane protein|transmembrane]] domain.<ref name="Johnson_2017" /><ref name="Xiao_2010">{{cite journal|date=July 2010|title=Bestrophins and retinopathies|journal=Pflugers Archiv|volume=460|issue=2|pages=559–69|doi=10.1007/s00424-010-0821-5|pmid=20349192|vauthors=Xiao Q, Hartzell HC, Yu K}}</ref> The pore is lined with various [[Chemical polarity|nonpolar]], [[Hydrophobe|hydrophobic]] amino acids which help to act as a selectivity filter by forming at least 15 [[Binding site|binding sites]] for each anion.<ref name="Johnson_2017" /><ref name="Kunzelmann_2015">{{cite journal|date=September 2015|title=TMEM16, LRRC8A, bestrophin: chloride channels controlled by Ca(2+) and cell volume|journal=Trends in Biochemical Sciences|volume=40|issue=9|pages=535–43|doi=10.1016/j.tibs.2015.07.005|pmid=26254230|vauthors=Kunzelmann K}}</ref> Both the structure and the composition of the pore help to ensure that only small anions are able to move completely through the channel. The channel acts as two funnels working together in tandem. It begins with a semi-selective, narrow entryway for anions, and then opens to a larger, positively charged area which then leads to a narrower pathway that further limits the size of anions passing through the pore. A calcium clasp acts as a belting mechanism around the larger, middle section of the channel. Calcium ions control the opening and closing of the channel due to [[Conformational change|conformational changes]] caused by calcium binding at the C-terminus directly following the last transmembrane domain.<ref name="Johnson_2017" /><ref name="Xiao_2010" /> The structure of the [[Calcium-activated chloride channel|calcium-dependent chloride channel]], which is bestrophin 1, contributes greatly to the overall function of the channel.<ref name="Johnson_2017" />


== Function ==
BEST1 has been shown by two independent studies to be regulated by [[Microphthalmia-associated transcription factor]].<ref name="pmid17085443">{{cite journal | vauthors = Esumi N, Kachi S, Campochiaro PA, Zack DJ | title = VMD2 promoter requires two proximal E-box sites for its activity in vivo and is regulated by the MITF-TFE family | journal = The Journal of Biological Chemistry | volume = 282 | issue = 3 | pages = 1838–50 | date = January 2007 | pmid = 17085443 | doi = 10.1074/jbc.M609517200 }}</ref><ref name="pmidunknown">{{cite journal | vauthors = Hoek KS, Schlegel NC, Eichhoff OM, Widmer DS, Praetorius C, Einarsson SO, Valgeirsdottir S, Bergsteinsdottir K, Schepsky A, Dummer R, Steingrimsson E | title = Novel MITF targets identified using a two-step DNA microarray strategy | journal = Pigment Cell & Melanoma Research | volume = 21 | issue = 6 | pages = 665–76 | date = December 2008 | pmid = 19067971 | doi = 10.1111/j.1755-148X.2008.00505.x }}</ref>

BEST1 belongs to the bestrophin family of calcium-activated anion channels, which includes [[BEST2]], BEST3, and BEST4. Bestrophins are transmembrane (TM) proteins that share a homology region containing a high content of aromatic residues, including an invariant arg-phe-pro (RFP) motif. Bestrophins are believed to function as [[chloride channel]]s that may also serve as regulators of intracellular calcium signalling.<ref name="pmid18391176">{{cite journal|date=April 2008|title=Molecular physiology of bestrophins: multifunctional membrane proteins linked to best disease and other retinopathies|journal=Physiological Reviews|volume=88|issue=2|pages=639–72|doi=10.1152/physrev.00022.2007|pmid=18391176|vauthors=Hartzell HC, Qu Z, Yu K, Xiao Q, Chien LT}}</ref>


== Interactions ==
== Interactions ==

Revision as of 01:35, 1 April 2017

BEST1
Identifiers
AliasesBEST1, ARB, BEST, BMD, RP50, TU15B, VMD2, Bestrophin 1, Best1V1Delta2
External IDsOMIM: 607854; MGI: 1346332; HomoloGene: 37895; GeneCards: BEST1; OMA:BEST1 - orthologs
Orthologs
SpeciesHumanMouse
Entrez
Ensembl
UniProt
RefSeq (mRNA)

NM_011913

RefSeq (protein)

NP_036043

Location (UCSC)Chr 11: 61.95 – 61.97 MbChr 19: 9.96 – 9.98 Mb
PubMed search[3][4]
Wikidata
View/Edit HumanView/Edit Mouse

Bestrophin-1 is a protein that, in humans, is encoded by the BEST1 gene (RPD ID - 5T5N/4RDQ).[5][6][7]

Calcium-activated chloride channel bestrophin-1 (BEST1), triple mutant: I76A, F80A, F84A; in complex with an Fab antibody fragment, chloride, and calcium. From RCSB PDB.

The bestrophin family is comprised of four ancestrally linked genes (BEST1, BEST2, BEST3, and BEST4) that code for integral membrane proteins.[8] The bestrophins were first identified in humans by relating a BEST1 mutation with Best vitelliform macular dystrophy (BVMD).[9] Mutations in the BEST1 gene have been determined as the primary cause for at least five different degenerative retinal diseases.[9]

Structure in humans

Gene structure

The bestrophin genes share a conserved gene structure, with almost identical sizes of the 8 RFP-TM domain-encoding exons and highly conserved exon-intron boundaries. Each of the 4 bestrophin genes has a unique 3-prime end of variable length.[7][10][11]

BEST1 has been shown by two independent studies to be regulated by Microphthalmia-associated transcription factor.[12][13]

Protein structure

Bestrophin 1 is an integral membrane protein found only in the retinal pigment epithelium (RPE) of the eye.[14] Within the RPE layer, Best1 is primarily located on the basolateral plasma membrane. Protein crystallization structures indicate the primary ion channel function of Best1 as well as the calcium regulatory capabilities.[14][15]Bestrophin 1 consists of 585 amino acids and both N- and the C-termini are located within the cell.

Calcium-activated chloride channel bestrophin-1 (BEST1), triple mutant: I76A, F80A, F84A; in complex with an Fab antibody fragment, chloride, and calcium. From RCSB PDB

The structure of Best1 consists of five identical subunits that each span the membrane four times and form a continuous, funnel-shaped pore via the second transmembrane domain.[15][16] The pore is lined with various nonpolar, hydrophobic amino acids which help to act as a selectivity filter by forming at least 15 binding sites for each anion.[15][17] Both the structure and the composition of the pore help to ensure that only small anions are able to move completely through the channel. The channel acts as two funnels working together in tandem. It begins with a semi-selective, narrow entryway for anions, and then opens to a larger, positively charged area which then leads to a narrower pathway that further limits the size of anions passing through the pore. A calcium clasp acts as a belting mechanism around the larger, middle section of the channel. Calcium ions control the opening and closing of the channel due to conformational changes caused by calcium binding at the C-terminus directly following the last transmembrane domain.[15][16] The structure of the calcium-dependent chloride channel, which is bestrophin 1, contributes greatly to the overall function of the channel.[15]

Function

BEST1 belongs to the bestrophin family of calcium-activated anion channels, which includes BEST2, BEST3, and BEST4. Bestrophins are transmembrane (TM) proteins that share a homology region containing a high content of aromatic residues, including an invariant arg-phe-pro (RFP) motif. Bestrophins are believed to function as chloride channels that may also serve as regulators of intracellular calcium signalling.[18]

Interactions

Bestrophin 1 has been shown to interact with PPP2CA.[19][1]

References

  1. ^ a b c GRCh38: Ensembl release 89: ENSG00000167995Ensembl, May 2017
  2. ^ a b c GRCm38: Ensembl release 89: ENSMUSG00000037418Ensembl, May 2017
  3. ^ "Human PubMed Reference:". National Center for Biotechnology Information, U.S. National Library of Medicine.
  4. ^ "Mouse PubMed Reference:". National Center for Biotechnology Information, U.S. National Library of Medicine.
  5. ^ Stone EM, Nichols BE, Streb LM, Kimura AE, Sheffield VC (July 1992). "Genetic linkage of vitelliform macular degeneration (Best's disease) to chromosome 11q13". Nature Genetics. 1 (4): 246–50. doi:10.1038/ng0792-246. PMID 1302019.
  6. ^ Barro Soria R, Spitzner M, Schreiber R, Kunzelmann K (October 2009). "Bestrophin 1 enables Ca2+ activated Cl conductance in epithelia". The Journal of Biological Chemistry. 284 (43): 29405–12. doi:10.1074/jbc.M605716200. PMC 2785573. PMID 17003041.{{cite journal}}: CS1 maint: unflagged free DOI (link)
  7. ^ a b "Entrez Gene: BEST1 bestrophin 1".
  8. ^ Kunzelmann K (September 2015). "TMEM16, LRRC8A, bestrophin: chloride channels controlled by Ca(2+) and cell volume". Trends in Biochemical Sciences. 40 (9): 535–43. doi:10.1016/j.tibs.2015.07.005. PMID 26254230.
  9. ^ a b Johnson AA, Guziewicz KE, Lee CJ, Kalathur RC, Pulido JS, Marmorstein LY, Marmorstein AD (January 2017). "Bestrophin 1 and retinal disease". Progress in Retinal and Eye Research. doi:10.1016/j.preteyeres.2017.01.006. PMID 28153808.
  10. ^ Stöhr H, Marquardt A, Nanda I, Schmid M, Weber BH (April 2002). "Three novel human VMD2-like genes are members of the evolutionary highly conserved RFP-TM family". European Journal of Human Genetics. 10 (4): 281–4. doi:10.1038/sj.ejhg.5200796. PMID 12032738.
  11. ^ Tsunenari T, Sun H, Williams J, Cahill H, Smallwood P, Yau KW, Nathans J (October 2003). "Structure-function analysis of the bestrophin family of anion channels". The Journal of Biological Chemistry. 278 (42): 41114–25. doi:10.1074/jbc.M306150200. PMC 2885917. PMID 12907679.{{cite journal}}: CS1 maint: unflagged free DOI (link)
  12. ^ Esumi N, Kachi S, Campochiaro PA, Zack DJ (January 2007). "VMD2 promoter requires two proximal E-box sites for its activity in vivo and is regulated by the MITF-TFE family". The Journal of Biological Chemistry. 282 (3): 1838–50. doi:10.1074/jbc.M609517200. PMID 17085443.{{cite journal}}: CS1 maint: unflagged free DOI (link)
  13. ^ Hoek KS, Schlegel NC, Eichhoff OM, Widmer DS, Praetorius C, Einarsson SO, Valgeirsdottir S, Bergsteinsdottir K, Schepsky A, Dummer R, Steingrimsson E (December 2008). "Novel MITF targets identified using a two-step DNA microarray strategy". Pigment Cell & Melanoma Research. 21 (6): 665–76. doi:10.1111/j.1755-148X.2008.00505.x. PMID 19067971.
  14. ^ a b Strauss O, Neussert R, Müller C, Milenkovic VM (2012). "A potential cytosolic function of bestrophin-1". Advances in Experimental Medicine and Biology. 723: 603–10. doi:10.1007/978-1-4614-0631-0_77. PMID 22183384.
  15. ^ a b c d e Johnson AA, Guziewicz KE, Lee CJ, Kalathur RC, Pulido JS, Marmorstein LY, Marmorstein AD (January 2017). "Bestrophin 1 and retinal disease". Progress in Retinal and Eye Research. doi:10.1016/j.preteyeres.2017.01.006. PMID 28153808.
  16. ^ a b Xiao Q, Hartzell HC, Yu K (July 2010). "Bestrophins and retinopathies". Pflugers Archiv. 460 (2): 559–69. doi:10.1007/s00424-010-0821-5. PMID 20349192.
  17. ^ Kunzelmann K (September 2015). "TMEM16, LRRC8A, bestrophin: chloride channels controlled by Ca(2+) and cell volume". Trends in Biochemical Sciences. 40 (9): 535–43. doi:10.1016/j.tibs.2015.07.005. PMID 26254230.
  18. ^ Hartzell HC, Qu Z, Yu K, Xiao Q, Chien LT (April 2008). "Molecular physiology of bestrophins: multifunctional membrane proteins linked to best disease and other retinopathies". Physiological Reviews. 88 (2): 639–72. doi:10.1152/physrev.00022.2007. PMID 18391176.
  19. ^ Marmorstein LY, McLaughlin PJ, Stanton JB, Yan L, Crabb JW, Marmorstein AD (August 2002). "Bestrophin interacts physically and functionally with protein phosphatase 2A". The Journal of Biological Chemistry. 277 (34): 30591–7. doi:10.1074/jbc.M204269200. PMID 12058047.{{cite journal}}: CS1 maint: unflagged free DOI (link)

Further reading

External links

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