1rcm
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(New page: 200px<br /><applet load="1rcm" size="450" color="white" frame="true" align="right" spinBox="true" caption="1rcm, resolution 1.9Å" /> '''CRYSTAL STRUCTURE OF ...)
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Revision as of 23:21, 20 November 2007
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CRYSTAL STRUCTURE OF A UBIQUITIN-DEPENDENT DEGRADATION SUBSTRATE: A THREE-DISULFIDE FORM OF LYSOZYME
Overview
Covalent attachment of ubiquitin marks substrates for proteolysis, but, features that identify ubiquitination targets such as chicken egg white, lysozyme are poorly understood. Recognition of lysozyme first requires, reduction of Cys-6 Cys-127, one of its four native disulfide bonds, and, Cys-6,Cys-127-carboxymethylated (6,127-rcm) lysozyme can mimic this, three-disulfide intermediate. The 6,127-rcm form of lysozyme is known to, retain a substantially native-like conformation in solution, and we, demonstrate that it is this folded structure that is recognized for, ubiquitination. Because native lysozyme is not a substrate, differences, between the native and three-disulfide structures must include features, responsible for selective ubiquitination. The 1.9-A resolution crystal, structure of 6,127-rcm-lysozyme, reported here, affords a view of this, ubiquitin-dependent degradation substrate. Two conformers of, 6,127-rcm-lysozyme were obtained in the crystal. These differ uniquely, from crystal forms of native lysozyme by displacement of the C-terminal, residues. The structures suggest that localized unfolding at the C, terminus of three-disulfide lysozyme allows the complex of E3 alpha, (ubiquitin-protein ligase) and E2 (ubiquitin-carrier protein) to bind to a, surface that includes Lys-1 and the putative ubiquitination site Lys-13., From this we infer that the N-terminal and internal substrate recognition, sites on the E3 alpha.E2 complex are separated by approximately 20 A.
About this Structure
1RCM is a Single protein structure of sequence from Gallus gallus with ACY as ligand. Active as Lysozyme, with EC number 3.2.1.17 Full crystallographic information is available from OCA.
Reference
Crystal structure of a ubiquitin-dependent degradation substrate: a three-disulfide form of lysozyme., Hill CP, Johnston NL, Cohen RE, Proc Natl Acad Sci U S A. 1993 May 1;90(9):4136-40. PMID:8387211
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