Nature Structural Biology
9, 906 - 911 (2002)
Published online: 11 November 2002; | doi:10.1038/nsb869
Structural analysis of the adaptor protein ClpS in complex with the N-terminal domain of ClpAKornelius Zeth1, 2, Raimond B. Ravelli2, Klaus Paal3, Stephen Cusack2, Bernd Bukau3, 4
& David A. Dougan3, 41
MPI für Biochemie, Abteilung Membranbiochemie, Am Klopferspitz 18a, D-82152 Martinsried, Germany. 2
EMBL outstation Grenoble, 6, rue Jules Horowitz, BP181, 38042 Grenoble Cedex 9, France. 3
Institut für Biochemie, Universität Freiburg, Hermann-Herder-Strasse 7, D-79104 Freiburg, Germany. 4
Present address: ZMBH, Universität Heidelberg, Im Neuenheimer Feld 282, Heidelberg D-69120, Germany.
Correspondence should be addressed to Kornelius Zeth zeth@biochem.mpg.de or David A. Dougan d.dougan@zmbh.uni-heidelberg.deIn Escherichia coli, protein degradation is performed by several proteolytic machines, including ClpAP. Generally, the substrate specificity of these machines is determined by chaperone components, such as ClpA. In some cases, however, the specificity is modified by adaptor proteins, such as ClpS. Here we report the 2.5 Å resolution crystal structure of ClpS in complex with the N-terminal domain of ClpA. Using mutagenesis, we demonstrate that two contact residues (Glu79 and Lys 84) are essential not only for ClpAS complex formation but also for ClpAPS-mediated substrate degradation. The corresponding residues are absent in the chaperone ClpB, providing a structural rationale for the unique specificity shown by ClpS despite the high overall similarity between ClpA and ClpB. To determine the location of ClpS within the ClpA hexamer, we modeled the N-terminal domain of ClpA onto a structurally defined, homologous AAA+ protein. From this model, we proposed a molecular mechanism to explain the ClpS-mediated switch in ClpA substrate specificity.
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