Overlapping recognition determinants within the ssrA degradation tag allow modulation of proteolysis.
The ssrA tag, an 11-aa peptide added to the C terminus of proteins stalled during translation, targets proteins for degradation by ClpXP and ClpAP. Mutational analysis of the ssrA tag reveals independent, but overlapping determinants for its interactions with ClpX, ClpA, and SspB, a specificity-enhancing factor for ClpX. ClpX interacts with residues 9-11 at the C terminus of the tag, whereas ClpA recognizes positions 8-10 in addition to residues 1-2 at the N terminus. SspB interacts with residues 1-4 and 7, N-terminal to the ClpX-binding determinants, but overlapping the ClpA determinants. As a result, SspB and ClpX work together to recognize ssrA-tagged substrates efficiently, whereas SspB inhibits recognition of these substrates by ClpA. Thus, dissection of the recognition signals within the ssrA tag provides insight into how multiple proteins function in concert to modulate proteolysis.
Flynn
J M
JM
Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
Levchenko
I
I
Seidel
M
M
Wickner
S H
SH
Sauer
R T
RT
Baker
T A
TA
D000074183:ATPases Associated with Diverse Cellular Activities; D000251:Adenosine Triphosphatases / Q000378:metabolism*; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000378:metabolism*; D049071:Endopeptidase Clp; D029968:Escherichia coli Proteins; D049452:Green Fluorescent Proteins; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D018832:Molecular Chaperones; D008969:Molecular Sequence Data; D016296:Mutagenesis; D012329:RNA, Bacterial / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D012697:Serine Endopeptidases / Q000378:metabolism*; D014157:Transcription Factors
D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D008164:Luminescent Proteins; D018832:Molecular Chaperones; D012329:RNA, Bacterial; D011993:Recombinant Fusion Proteins; C119761:SsrB protein, Salmonella typhimurium; D014157:Transcription Factors; C096222:tmRNA; D049452:Green Fluorescent Proteins; D012697:Serine Endopeptidases; D049071:Endopeptidase Clp; D000251:Adenosine Triphosphatases; C088072:ClpX protein, E coli; D000074183:ATPases Associated with Diverse Cellular Activities