Proteasomes begin ornithine decarboxylase digestion at the C terminus

Zhang, M., MacDonald, A. I., Hoyt, M. A. and Coffino, P. (2004) Proteasomes begin ornithine decarboxylase digestion at the C terminus. Journal of Biological Chemistry, 279(20), pp. 20959-20965. (doi: 10.1074/jbc.M314043200) (PMID:15016805)

Full text not currently available from Enlighten.

Abstract

Proteasomes denature folded protein substrates and thread them through a narrow pore that leads to the sequestered sites of proteolysis. Whether a protein substrate initiates insertion from its N or C terminus or in a random orientation has not been determined for any natural substrate. We used the labile enzyme ornithine decarboxylase (ODC), which is recognized by the proteasome via a 37-residue C-terminal tag, to answer this question. Three independent approaches were used to assess orientation as follows. 1) The 461-residue ODC protein chain was interrupted at position 305. The C-terminal fragment was degraded by purified proteasomes, but because processivity requires continuity of the polypeptide chain, the N-terminal fragment was spared. 2) A proteasome-inhibitory viral sequence prevented degradation when introduced near the C terminus but not when inserted elsewhere in ODC. 3) A bulky tightly folded protein obstructed in vivo degradation most effectively when positioned near the C terminus. These data demonstrate that the proteasome initiates degradation of this native substrate at the C terminus. The co-localization of entry site and degradation tag to the ODC C terminus suggests that recognition tags determine the site for initiating entry. Flexibility of a polypeptide terminus may promote the initiation of degradation.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:MacDonald, Dr Alasdair
Authors: Zhang, M., MacDonald, A. I., Hoyt, M. A., and Coffino, P.
College/School:College of Medical Veterinary and Life Sciences > School of Infection & Immunity
Journal Name:Journal of Biological Chemistry
Publisher:American Society for Biochemistry and Molecular Biology
ISSN:0021-9258
ISSN (Online):1083-351X

University Staff: Request a correction | Enlighten Editors: Update this record