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Modification of PATase by L/F‐transferase generates a ClpS‐dependent N‐end rule substrate in Escherichia coli
Author(s) -
Ninnis Robert L,
Spall Sukhdeep K,
Talbo Gert H,
Truscott Kaye N,
Dougan David A
Publication year - 2009
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1038/emboj.2009.134
Subject(s) - biology , escherichia coli , transferase , substrate (aquarium) , substrate specificity , escherichia coli proteins , microbiology and biotechnology , genetics , biochemistry , enzyme , gene , ecology
The N‐end rule pathway is conserved from bacteria to man and determines the half‐life of a protein based on its N‐terminal amino acid. In Escherichia coli , model substrates bearing an N‐degron are recognised by ClpS and degraded by ClpAP in an ATP‐dependent manner. Here, we report the isolation of 23 ClpS‐interacting proteins from E. coli . Our data show that at least one of these interacting proteins—putrescine aminotransferase (PATase)—is post‐translationally modified to generate a primary N‐degron. Remarkably, the N‐terminal modification of PATase is generated by a new specificity of leucyl/phenylalanyl‐tRNA‐protein transferase (LFTR), in which various combinations of primary destabilising residues (Leu and Phe) are attached to the N‐terminal Met. This modification (of PATase), by LFTR, is essential not only for its recognition by ClpS, but also determines the stability of the protein in vivo . Thus, the N‐end rule pathway, through the ClpAPS‐mediated turnover of PATase may have an important function in putrescine homeostasis. In addition, we have identified a new element within the N‐degron, which is required for substrate delivery to ClpA.