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Alternating translocation of protein substrates from both ends of ClpXP protease
Author(s) -
Ortega Joaquin,
Lee Hyun Sook,
Maurizi Michael R.,
Steven Alasdair C.
Publication year - 2002
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 - 10.1093/emboj/cdf483
Subject(s) - chromosomal translocation , biology , protease , biophysics , chaperone (clinical) , microbiology and biotechnology , biochemistry , crystallography , enzyme , chemistry , gene , medicine , pathology
In ClpXP protease complexes, hexameric rings of the ATP‐dependent ClpX chaperone stack on one or both faces of the double‐heptameric rings of ClpP. We used electron microscopy to record the initial binding of protein substrates to ClpXP and their accumulation inside proteolytically inactive ClpP. Proteins with N‐ or C‐terminal recognition motifs bound to complexes at the distal surface of ClpX and, upon addition of ATP, were translocated to ClpP. With a partially translocated substrate, the non‐translocated portion remained on the surface of ClpX, aligned with the central axis of the complex, confirming that translocation proceeds through the axial channel of ClpXP. Starting with substrate bound on both ends, most complexes translocated substrate from only one end, and rarely (<5%) from both ends. We propose that translocation from one side is favored for two reasons: initiation of translocation is infrequent, making the probability of simultaneous initiation low; and, further, the presence of protein within the cis side translocation channel or within ClpP generates an inhibitory signal blocking translocation from the trans side.