| Structural highlights
1fmi is a 1 chain structure with sequence from Homo sapiens. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance.
| | Ligands: | ,
| | Activity: | Mannosyl-oligosaccharide 1,2-alpha-mannosidase, with EC number 3.2.1.113 |
| Resources: | FirstGlance, OCA, RCSB, PDBsum |
Disease
[MA1B1_HUMAN] Defects in MAN1B1 are the cause of mental retardation autosomal recessive type 15 (MRT15) [MIM:614202]. Mental retardation is characterized by significantly below average general intellectual functioning associated with impairments in adaptative behavior and manifested during the developmental period.[1]
Function
[MA1B1_HUMAN] Involved in glycoprotein quality control targeting of misfolded glycoproteins for degradation. It primarily trims a single alpha-1,2-linked mannose residue from Man(9)GlcNAc(2) to produce Man(8)GlcNAc(2), but at high enzyme concentrations, as found in the ER quality control compartment (ERQC), it further trims the carbohydrates to Man(5-6)GlcNAc(2).[2] [3]
Evolutionary Conservation
Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf.
Publication Abstract from PubMed
Endoplasmic reticulum (ER) class I alpha1,2-mannosidase (also known as ER alpha-mannosidase I) is a critical enzyme in the maturation of N-linked oligosaccharides and ER-associated degradation. Trimming of a single mannose residue acts as a signal to target misfolded glycoproteins for degradation by the proteasome. Crystal structures of the catalytic domain of human ER class I alpha1,2-mannosidase have been determined both in the presence and absence of the potent inhibitors kifunensine and 1-deoxymannojirimycin. Both inhibitors bind to the protein at the bottom of the active-site cavity, with the essential calcium ion coordinating the O-2' and O-3' hydroxyls and stabilizing the six-membered rings of both inhibitors in a (1)C(4) conformation. This is the first direct evidence of the role of the calcium ion. The lack of major conformational changes upon inhibitor binding and structural comparisons with the yeast alpha1, 2-mannosidase enzyme-product complex suggest that this class of inverting enzymes has a novel catalytic mechanism. The structures also provide insight into the specificity of this class of enzymes and provide a blueprint for the future design of novel inhibitors that prevent degradation of misfolded proteins in genetic diseases.
Structural basis for catalysis and inhibition of N-glycan processing class I alpha 1,2-mannosidases.,Vallee F, Karaveg K, Herscovics A, Moremen KW, Howell PL J Biol Chem. 2000 Dec 29;275(52):41287-98. PMID:10995765[4]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
See Also
References
- ↑ Rafiq MA, Kuss AW, Puettmann L, Noor A, Ramiah A, Ali G, Hu H, Kerio NA, Xiang Y, Garshasbi M, Khan MA, Ishak GE, Weksberg R, Ullmann R, Tzschach A, Kahrizi K, Mahmood K, Naeem F, Ayub M, Moremen KW, Vincent JB, Ropers HH, Ansar M, Najmabadi H. Mutations in the alpha 1,2-mannosidase gene, MAN1B1, cause autosomal-recessive intellectual disability. Am J Hum Genet. 2011 Jul 15;89(1):176-82. doi: 10.1016/j.ajhg.2011.06.006. PMID:21763484 doi:10.1016/j.ajhg.2011.06.006
- ↑ Herscovics A, Romero PA, Tremblay LO. The specificity of the yeast and human class I ER alpha 1,2-mannosidases involved in ER quality control is not as strict previously reported. Glycobiology. 2002 Apr;12(4):14G-15G. PMID:12090241
- ↑ Avezov E, Frenkel Z, Ehrlich M, Herscovics A, Lederkremer GZ. Endoplasmic reticulum (ER) mannosidase I is compartmentalized and required for N-glycan trimming to Man5-6GlcNAc2 in glycoprotein ER-associated degradation. Mol Biol Cell. 2008 Jan;19(1):216-25. Epub 2007 Nov 14. PMID:18003979 doi:10.1091/mbc.E07-05-0505
- ↑ Vallee F, Karaveg K, Herscovics A, Moremen KW, Howell PL. Structural basis for catalysis and inhibition of N-glycan processing class I alpha 1,2-mannosidases. J Biol Chem. 2000 Dec 29;275(52):41287-98. PMID:10995765 doi:10.1074/jbc.M006927200
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