X-ray structure of the catalytic domain of UCH-L5, a proteasome-associated deubiquitinase
Abstract
Ubiquitin Carboxy-terminal hydrolase L5 (UCH-L5, also known as Uch37) is deubiquitinating enzyme (DUB) belonging to the carboxy terminal family of cysteine proteases. It has been determined that UCH-L5 is very similar to it family members in terms of its sequence composition, but very different in its structure compared to UCH-L1 and UCH-L3, which suggests very different functions from its family members. To fully understand how DUBs interact with ubiquitin signaling, the structure and function of these enzymes need to be studied. More so, because of recent findings of its interaction with Rpn 13, UCH-L5 presents an excellent case for structural characterization of the regulation of DUB activity. To do this, a construct of the catalytic truncated domains were cloned from the human genome, expressed and purified, then crystallized and studied using x-ray crystallography so that the structural basis of UCH-L5 activation could be investigated. The structure reveals that the free form of UCH-L5 is auto inhibited since the N terminus of the enzyme blocks the active site. In addition, the so called “cross over” loop adopts a confirmation in which it seems is designed to preclude polyubiquitin chains as a substrate. Based on these results, it appears as though, during binding and processing of ubiquitin chains, there are dramatic conformational changes to accommodate substrates.
Degree
M.S.
Advisors
Das, Purdue University.
Subject Area
Biochemistry|Biophysics
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