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Crystal Structure of the mammalian COPII-coat protein Sec23/24 bound to the transport signal sequence of syntaxin 5
Structural highlights
DiseaseSC23A_HUMAN Defects in SEC23A are the cause of craniolenticulosutural dysplasia (CLSD) [MIM:607812; also known as cranio-lenticulo-sutural dysplasia. CLSD is an autosomal recessive syndrome characterized by late-closing fontanels, sutural cataracts, facial dysmorphisms and skeletal defects.[1] FunctionSC23A_HUMAN Component of the COPII coat, that covers ER-derived vesicles involved in transport from the endoplasmic reticulum to the Golgi apparatus. COPII acts in the cytoplasm to promote the transport of secretory, plasma membrane, and vacuolar proteins from the endoplasmic reticulum to the Golgi complex. 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 PubMedGenomic analysis shows that the increased complexity of trafficking pathways in mammalian cells involves an expansion of the number of SNARE, Rab and COP proteins. Thus, the human genome encodes four forms of Sec24, the cargo selection subunit of the COPII vesicular coat, and this is proposed to increase the range of cargo accommodated by human COPII-coated vesicles. In this study, we combined X-ray crystallographic and biochemical analysis with functional assays of cargo packaging into COPII vesicles to establish molecular mechanisms for cargo discrimination by human Sec24 subunits. A conserved IxM packaging signal binds in a surface groove of Sec24c and Sec24d, but the groove is occluded in the Sec24a and Sec24b subunits. Conversely, LxxLE class transport signals and the DxE signal of VSV glycoprotein are selectively bound by Sec24a and Sec24b subunits. A comparative analysis of crystal structures of the four human Sec24 isoforms establishes the structural determinants for discrimination among these transport signals, and provides a framework to understand how an expansion of coat subunits extends the range of cargo proteins packaged into COPII-coated vesicles. Structural basis of cargo membrane protein discrimination by the human COPII coat machinery.,Mancias JD, Goldberg J EMBO J. 2008 Nov 5;27(21):2918-28. Epub 2008 Oct 9. PMID:18843296[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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