Structural basis of substrate selection by ubiquitin carboxyl terminal hydrolases

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Publication Type dissertation
School or College School of Medicine
Department Biochemistry
Author Johnston, Steven Curtis
Title Structural basis of substrate selection by ubiquitin carboxyl terminal hydrolases
Date 1998-06
Description The ubiquitin carboxyl terminal hydrolases (UCHs) are a family of cysteine proteases that catalyze the removal of adducts to the C-terminus of the ubiquitin. Ubiquitin is a very highly conserved protein in eukaryotic organisms where it functions, in part, as a signal targeting protein for proteolysis at the 26S protease. One product of the deubiquitinating reaction is ubiquitin with a C-terminal COOH, a feature necessary for activation of ubiquitin and conjugation to substrates. The work here describes the three dimensional structures of two UCHs determined by X-ray crystallography. One of these structures is of the unliganded human UCH-L3 enzyme, and the other is a complex of the yeast Yuhl enzyme bound to the substrate analogue ubiquitin aldehyde (Ubal). The UCH fold is comprised of a central antiparallel p-sheet which is packed against a-helices on both sides. This structure resembles that of the papain family of cysteine proteases; an observation that the UCH-L3 active site is comprised of a cysteine-histidine-aspartate catalytic triad and a glutamine oxyanion hole. The Yuhl-Ubal complex structure mimics the tetrahedral intermediate of the enzymatic reaction, with a covalent bond formed between the C-terminal carbon atom of Ubal and the active site cysteine of Yuhl. The interaction seen between Yuhl and Ubal, which is extensive and includes numerous hydrogen bonds and van der Waals interactions, explains the specificity of UCH enzymes for ubiquitin adducts. Differences between UCH-L3 and Yuhl-Ubal structures suggest that the enzyme active site is sequestered in the absence of substrate, and that the energy of binding ubiquitin is coupled to formation of an active conformation. One of the apparent conformational changes upon binding Ubal is the ordering of a loop tightly across the active-site cleft, such that substrates are probably required to orient their C-terminal adducts through a narrow opening.
Type Text
Publisher University of Utah
Subject Glutamine Oxyanion Hole
Subject MESH Cysteine Endopeptidases; Structure-Activity Relationship
Dissertation Institution University of Utah
Dissertation Name PhD
Language eng
Relation is Version of Digital reproduction of "The structural basis of substrate selection by ubiquitin carboxyl terminal hydrolases". Spencer S. Eccles Health Sciences Library. Print version of "The structural basis of substrate selection by ubiquitin carboxyl terminal hydrolases". available at J. Willard Marriott Library Special Collection. QP6.5 1998 .J64.
Rights Management © Steven Curtis Johnston.
Format Medium application/pdf
Format Extent 5,087,002 bytes
Identifier undthes,4555
Source Original: University of Utah Spencer S. Eccles Health Sciences Library (no longer available).
Master File Extent 5,087,059 bytes
ARK ark:/87278/s61j9cnt
Setname ir_etd
Date Created 2012-04-24
Date Modified 2012-04-24
ID 191311
Reference URL https://collections.lib.utah.edu/ark:/87278/s61j9cnt