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The Crystal Structure of a E280A Mutant of the Catalytic Domain of AMSH
Structural highlights
DiseaseSTABP_HUMAN Microcephaly-capillary malformation syndrome. The disease is caused by mutations affecting the gene represented in this entry. FunctionSTABP_HUMAN Zinc metalloprotease that specifically cleaves 'Lys-63'-linked polyubiquitin chains. Does not cleave 'Lys-48'-linked polyubiquitin chains (By similarity). Plays a role in signal transduction for cell growth and MYC induction mediated by IL-2 and GM-CSF. Potentiates BMP (bone morphogenetic protein) signaling by antagonizing the inhibitory action of SMAD6 and SMAD7. Has a key role in regulation of cell surface receptor-mediated endocytosis and ubiquitin-dependent sorting of receptors to lysosomes. Endosomal localization of STAMBP is required for efficient EGFR degradation but not for its internalization (By similarity). Involved in the negative regulation of PI3K-AKT-mTOR and RAS-MAP signaling pathways.[1] [2] [3] [4] [5] Publication Abstract from PubMedAMSH plays a critical role in the ESCRT (endosomal sorting complexes required for transport) machinery, which facilitates the down-regulation and degradation of cell-surface receptors. It displays a high level of specificity toward cleavage of Lys63-linked polyubiquitin chains, the structural basis of which has been understood recently through the crystal structure of a highly related, but ESCRT-independent, protein AMSH-LP (AMSH-like protein). We have determined the X-ray structure of two constructs representing the catalytic domain of AMSH: AMSH244, the JAMM (JAB1/MPN/MOV34)-domain-containing polypeptide segment from residues 244 to 424, and AMSH219(E280A), an active-site mutant, Glu280 to Ala, of the segment from 219 to 424. In addition to confirming the expected zinc coordination in the protein, the structures reveal that the catalytic domains of AMSH and AMSH-LP are nearly identical; however, guanidine-hydrochloride-induced unfolding studies show that the catalytic domain of AMSH is thermodynamically less stable than that of AMSH-LP, indicating that the former is perhaps structurally more plastic. Much to our surprise, in the AMSH219(E280A) structure, the catalytic zinc was still held in place, by the compensatory effect of an aspartate from a nearby loop moving into a position where it could coordinate with the zinc, once again suggesting the plasticity of AMSH. Additionally, a model of AMSH244 bound to Lys63-linked diubiquitin reveals a type of interface for the distal ubiquitin significantly different from that seen in AMSH-LP. Altogether, we believe that our data provide important insight into the structural difference between the two proteins that may translate into the difference in their biological function. Structural and Thermodynamic Comparison of the Catalytic Domain of AMSH and AMSH-LP: Nearly Identical Fold but Different Stability.,Davies CW, Paul LN, Kim MI, Das C J Mol Biol. 2011 Oct 21;413(2):416-29. Epub 2011 Aug 24. PMID:21888914[6] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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