Autoinhibitory interactions between the PDZ2 and C-terminal domains in the scaffolding protein NHERF1.
Na(+)/H(+) exchanger regulatory factor (NHERF1) is a signaling adaptor protein comprising two PDZ domains and a C-terminal ezrin-binding (EB) motif. To understand the role of intramolecular interactions in regulating its binding properties, we characterized the complex between the second PDZ domain PDZ2 and the C-terminal 242-358 fragment of NHERF1 using NMR and fluorescence methods. NMR chemical shift and relaxation data implicate 11 C-terminal residues in binding and, together with a thermodynamic analysis of mutant proteins, indicate that the EB region becomes helical when bound to PDZ2. Both specific contacts between PDZ2 and EB as well as nonspecific interactions involving a 100-residue flexible linker contribute to stabilizing two structurally distinct closed conformations of NHERF1. The affinity of mutant proteins for an extrinsic ligand is inversely related to the helix-forming propensity of the EB motif. The findings provide a structural framework for understanding how autoinhibitory interactions modulated the binding properties of NHERF1.
Cheng
Hong
H
Fox Chase Cancer Center, Philadelphia, PA 19111, USA.
Li
Jianquan
J
Fazlieva
Ruzaliya
R
Dai
Zhongping
Z
Bu
Zimei
Z
Roder
Heinrich
H
D020816:Amino Acid Motifs; D001665:Binding Sites; D008958:Models, Molecular; D019906:Nuclear Magnetic Resonance, Biomolecular; D054731:PDZ Domains; D010750:Phosphoproteins / Q000737:chemistry* / Q000378:metabolism*; D011487:Protein Conformation; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017923:Sodium-Hydrogen Exchangers / Q000737:chemistry* / Q000378:metabolism*; D013816:Thermodynamics
D010750:Phosphoproteins; D011994:Recombinant Proteins; D017923:Sodium-Hydrogen Exchangers; C093376:sodium-hydrogen exchanger regulatory factor