UbiquitinProteasome Pathway

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Ubiquitin-Proteasome Pathway
SIGMA-ALDRICH
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Ubiquitin-Proteasome Pathway Intracellular
proteolytic systems recognize and destroy
misfolded or damaged proteins, unassembled
polypeptide chains, and short-lived regulatory
proteins. There are several mechanisms for
protein degradation within cells. Two systems
that play important roles in proteolysis
resulting from cell stress are the calpain
proteases and the ubiquitin-proteasome pathway.
The ubiquitin-proteasome pathway functions widely
in intracellular protein turnover. It plays a
central role in degradation of short-lived and
regulatory proteins important in a variety of
basic cellular processes, including regulation of
the cell cycle, modulation of cell surface
receptors and ion channels, and antigen
processing and presentation. The pathway employs
an enzymatic cascade by which multiple ubiquitin
molecules are covalently attached to the protein
substrate. The polyubiquitin modification marks
the protein for destruction and directs it to the
26S proteasome complex for degradation.
References Sommer, T., et al., Compartment -
specific functions of the ubiquitin - proteasome
pathway. Rev. Physiol. Biochem. Pharmacol., 142,
97-160 (2001). Doskeland, A.P., and Flatmark, T.,
Conjugation of phenylalanine hydroxylase with
polyubiquitin chains catalysed by rat liver
enzymes. Biochim. Biophys. Acta., 1547, 379-386
(2001). Hartmann-Petersen, R., et al., Quaternary
structure of the ATPase complex of human 26S
proteasomes determined by chemical cross-linking.
Arch. Biochem. Biophys., 386, 89-94
(2001). Brooks, P., et al., Subcellular
localization of proteasomes and their regulatory
complexes in mammalian cells. Biochem. J., 346,
155-161 (2000).