4m92 | pdb_00004m92
Crystal structure of hN33/Tusc3-peptide 2
Structural highlights
Disease[TUSC3_HUMAN] Autosomal recessive nonsyndromic intellectual deficit. The disease is caused by mutations affecting the gene represented in this entry. [IRPL1_HUMAN] Defects in IL1RAPL1 are the cause of mental retardation X-linked type 21 (MRX21) [MIM:300143]. Mental retardation is a mental disorder characterized by significantly sub-average general intellectual functioning associated with impairments in adaptative behavior and manifested during the developmental period. Non-syndromic mental retardation patients do not manifest other clinical signs.[1] [2] Function[TUSC3_HUMAN] Magnesium transporter. May be involved in N-glycosylation through its association with N-oligosaccharyl transferase.[3] [IRPL1_HUMAN] May regulate secretion and presynaptic differentiation through inhibition of the activity of N-type voltage-gated calcium channel. May activate the MAP kinase JNK. Plays a role in presynaptic and postsynaptic differentiation and dendritic spine formation in neurons.[4] [5] Publication Abstract from PubMedN-linked glycosylation of proteins in the endoplasmic reticulum (ER) is essential in eukaryotes and catalyzed by oligosaccharyl transferase (OST). Human OST is a hetero-oligomer of seven subunits. The subunit N33/Tusc3 is a tumor suppressor candidate, and defects in the subunit N33/Tusc3 are linked with nonsyndromic mental retardation. Here, we show that N33/Tusc3 possesses a membrane-anchored N-terminal thioredoxin domain located in the ER lumen that may form transient mixed disulfide complexes with OST substrates. X-ray structures of complexes between N33/Tusc3 and two different peptides as model substrates reveal a defined peptide-binding groove adjacent to the active site that can accommodate peptides in opposite orientations. Structural and biochemical data show that N33/Tusc3 prefers peptides bearing a hydrophobic residue two residues away from the cysteine forming the mixed disulfide with N33/Tusc3. Our results support a model in which N33/Tusc3 increases glycosylation efficiency for a subset of human glycoproteins by slowing glycoprotein folding. Structural basis of substrate specificity of human oligosaccharyl transferase subunit n33/tusc3 and its role in regulating protein N-glycosylation.,Mohorko E, Owen RL, Malojcic G, Brozzo MS, Aebi M, Glockshuber R Structure. 2014 Apr 8;22(4):590-601. doi: 10.1016/j.str.2014.02.013. Epub 2014, Mar 27. PMID:24685145[6] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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