Saposin: Difference between revisions

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~~{{STRUCTURE_2dob| PDB~~=2dob ~~| SIZE~~=~~400| SCENE~~= |right~~|CAPTION~~=Human saposin A complex with Ca+2 ~~ion~~, [[~~2dob~~]] }}

== Function ==

'''Saposin''' (Sap) is a small protein which functions as activator of lipid-degrading enzymes. They act by isolating the lipid substrate from the membrane. Sap is synthesized as a precursor – prosaposin – which contain 4 SapB active domains (cleaved to saposin A,B,C and D) and 2 SapA domains which are cleaved off<ref>PMID:2001789</ref>. See also [[Lipid metabolism]].

'''Saposin''' ~~(Sap) is a small protein which functions as activator~~ of ~~lipid~~-~~degrading enzymes. They act~~ by ~~isolating the lipid substrate from the membrane. Sap is synthesized as a precursor – prosaposin – which contain 4 SapB active domains~~ and ~~2 SapA domains which are cleaved off~~. For more details see [[Molecular Playground/Saposin C]].

*'''Saposin A and C''' stimulate hydrolysis of methylumbelliferyl β-galactoside by β-glucosylceramidase and of galactocerebrocide by β-galactosylceramidase<ref>PMID:2717620</ref>. For more details see [[Molecular Playground/Saposin C]].

*'''Saposin B''' facilitates lipid binding to CD1d<ref>PMID:17372201</ref>.

*'''Saposin D''' stimulates acid ceramidase activity<ref>PMID:8203897</ref>.

== Disease ==

Mutations in saposin B are autosomal recessive trait resulting in clinical metachromatic leukodystrophy<ref>PMID:17616409</ref>. Mutations in saposin D cause urinary system defects<ref>PMID:15345707</ref>.

</StructureSection>

== 3D Structures of Saposin ==

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{{#tree:id=OrganizedByTopic|openlevels=0|

*Saposin A

*Saposin A residues 60-143

**[[2dob]] – hSapA ~~residues 60-140~~ – human

**[[2dob]], [[4uex]] – hSapA – human

**[[4ddj]] – hSapA + LDAO

**[[7p4d]] – mSapA – mouse

**[[5nxb]] – mSapA + galactocerebrosidase

*Saposin A residues 1-81

**[[6d80]] – hSapA + mitochondrial calcium uniporter

*Saposin B

**[[1n69]] – hSapB + lipid

**[[1n69]] – hSapB + lipid

**[[4v2o]] – hSapB + chloroquine

*Saposin C

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**[[3bqp]], [[3bqq]], [[2r1q]], [[2rb3]] - hSapD residues 405-484

**[[5u85]] - mSapD residues 438-519

}}

== References ==

[[Category:Topic Page]]

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@@ Line 1: / Line 1: @@
-{{STRUCTURE_2dob|  PDB=2dob  | SIZE=400| SCENE= |right|CAPTION=Human saposin A complex with Ca+2 ion, [[2dob]] }}
+<StructureSection load='2dob' size='350' side='right' scene='' caption='Human saposin A complex with Ca+2 [[2dob]]'>
+== Function ==
+'''Saposin''' (Sap) is a small protein which functions as activator of lipid-degrading enzymes.  They act by isolating the lipid substrate from the membrane.  Sap is synthesized as a precursor – prosaposin – which contain 4 SapB active domains (cleaved to saposin A,B,C and D) and 2 SapA domains which are cleaved off<ref>PMID:2001789</ref>. See also [[Lipid metabolism]].
-'''Saposin''' (Sap) is a small protein which functions as activator of lipid-degrading enzymes.  They act by isolating the lipid substrate from the membrane.  Sap is synthesized as a precursor – prosaposin – which contain 4 SapB active domains and 2 SapA domains which are cleaved off.  For more details see [[Molecular Playground/Saposin C]].
+*'''Saposin A and C''' stimulate hydrolysis of methylumbelliferyl β-galactoside by β-glucosylceramidase and of galactocerebrocide by β-galactosylceramidase<ref>PMID:2717620</ref>.  For more details see [[Molecular Playground/Saposin C]].<br />
+*'''Saposin B''' facilitates lipid binding to CD1d<ref>PMID:17372201</ref>.<br />
+*'''Saposin D''' stimulates acid ceramidase activity<ref>PMID:8203897</ref>.<br />
+== Disease ==
+Mutations in saposin B are autosomal recessive trait resulting in clinical metachromatic leukodystrophy<ref>PMID:17616409</ref>. Mutations in saposin D cause urinary system defects<ref>PMID:15345707</ref>.
+</StructureSection>
 == 3D Structures of Saposin ==
@@ Line 8: / Line 15: @@
 {{#tree:id=OrganizedByTopic|openlevels=0|
-*Saposin A
+*Saposin A residues 60-143
-**[[2dob]] – hSapA residues 60-140 – human<br />
+**[[2dob]], [[4uex]] – hSapA  – human<br />
 **[[4ddj]] – hSapA + LDAO<br />
+**[[7p4d]] – mSapA – mouse<br />
+**[[5nxb]] – mSapA + galactocerebrosidase <br />
+*Saposin A residues 1-81
+**[[6d80]] – hSapA + mitochondrial calcium uniporter<br />
 *Saposin B
-**[[1n69]] – hSapB + lipid
+**[[1n69]] – hSapB + lipid<br />
+**[[4v2o]] – hSapB + chloroquine<br />
 *Saposin C
@@ Line 25: / Line 39: @@
 **[[3bqp]], [[3bqq]], [[2r1q]], [[2rb3]] - hSapD residues 405-484<br />
+**[[5u85]] - mSapD residues 438-519<br />
 }}
+== References ==
+<references/>
 [[Category:Topic Page]]