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| {{STRUCTURE_2dob| PDB=2dob | SIZE=400| SCENE= |right|CAPTION=Human saposin A complex with Ca+2 ion, [[2dob]] }}
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| | <StructureSection load='2dob' size='350' side='right' scene='' caption='Human saposin A complex with Ca+2 [[2dob]]'> |
| == Function == | | == 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>. | | '''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>. |
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| == Disease == | | == 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>. | | 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 == | | == 3D Structures of Saposin == |
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Revision as of 21:37, 2 October 2017
| 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[1].
- Saposin A and C stimulate hydrolysis of methylumbelliferyl β-galactoside by β-glucosylceramidase and of galactocerebrocide by β-galactosylceramidase[2]. For more details see Molecular Playground/Saposin C.
- Saposin B facilitates lipid binding to CD1d[3].
- Saposin D stimulates acid ceramidase activity[4].
Disease
Mutations in saposin B are autosomal recessive trait resulting in clinical metachromatic leukodystrophy[5]. Mutations in saposin D cause urinary system defects[6].
- ↑ O'Brien JS, Kishimoto Y. Saposin proteins: structure, function, and role in human lysosomal storage disorders. FASEB J. 1991 Mar 1;5(3):301-8. PMID:2001789
- ↑ Morimoto S, Martin BM, Yamamoto Y, Kretz KA, O'Brien JS, Kishimoto Y. Saposin A: second cerebrosidase activator protein. Proc Natl Acad Sci U S A. 1989 May;86(9):3389-93. PMID:2717620
- ↑ Yuan W, Qi X, Tsang P, Kang SJ, Illarionov PA, Besra GS, Gumperz J, Cresswell P. Saposin B is the dominant saposin that facilitates lipid binding to human CD1d molecules. Proc Natl Acad Sci U S A. 2007 Mar 27;104(13):5551-6. Epub 2007 Mar 19. PMID:17372201 doi:https://dx.doi.org/10.1073/pnas.0700617104
- ↑ Azuma N, O'Brien JS, Moser HW, Kishimoto Y. Stimulation of acid ceramidase activity by saposin D. Arch Biochem Biophys. 1994 Jun;311(2):354-7. PMID:8203897
- ↑ Deconinck N, Messaaoui A, Ziereisen F, Kadhim H, Sznajer Y, Pelc K, Nassogne MC, Vanier MT, Dan B. Metachromatic leukodystrophy without arylsulfatase A deficiency: a new case of saposin-B deficiency. Eur J Paediatr Neurol. 2008 Jan;12(1):46-50. Epub 2007 Jul 5. PMID:17616409 doi:https://dx.doi.org/10.1016/j.ejpn.2007.05.004
- ↑ Matsuda J, Kido M, Tadano-Aritomi K, Ishizuka I, Tominaga K, Toida K, Takeda E, Suzuki K, Kuroda Y. Mutation in saposin D domain of sphingolipid activator protein gene causes urinary system defects and cerebellar Purkinje cell degeneration with accumulation of hydroxy fatty acid-containing ceramide in mouse. Hum Mol Genet. 2004 Nov 1;13(21):2709-23. Epub 2004 Sep 2. PMID:15345707 doi:https://dx.doi.org/10.1093/hmg/ddh281
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3D Structures of Saposin
Updated on 02-October-2017
{"openlevels":0}
- Saposin A
- Saposin B
- 1n69 – hSapB + lipid
- 4v2o – hSapB + chloroquine
- Saposin C
- Saposin D
References
