PMID: 14536076 , Related PDB ids: 1OU8, 1OU9, 1OUL

Authors:

Levchenko I, Grant RA, Wah DA, Sauer RT, Baker TA

Title:

Structure of a delivery protein for an AAA+ protease in complex with a peptide degradation tag.

Journal:

Mol Cell. 2003 Aug;12(2):365-72.

Abstract:

Substrate selection by AAA+ ATPases that function to unfold proteins or alter protein conformation is often regulated by delivery or adaptor proteins. SspB is a protein dimer that binds to the ssrA degradation tag and delivers proteins bearing this tag to ClpXP, an AAA+ protease, for degradation. Here, we describe the structure of the peptide binding domain of H. influenzae SspB in complex with an ssrA peptide at 1.6 A resolution. The ssrA peptides are bound in well-defined clefts located at the extreme ends of the SspB homodimer. SspB contacts residues within the N-terminal and central regions of the 11 residue ssrA tag but leaves the C-terminal residues exposed and positioned to dock with ClpX. This structure, taken together with biochemical analysis of SspB, suggests mechanisms by which proteins like SspB escort substrates to AAA+ ATPases and enhance the specificity and affinity of target recognition.