PDBsum entry 1j4o

Transferase

PDB id: 1j4o

Contents

Protein chain

151 a.a.

References listed in PDB file

Key reference

Title

Solution structures of two fha1-Phosphothreonine peptide complexes provide insight into the structural basis of the ligand specificity of fha1 from yeast rad53.

Authors

C.Yuan, S.Yongkiettrakul, I.J.Byeon, S.Zhou, M.D.Tsai.

Ref.

J Mol Biol, 2001, 314, 563-575. [DOI no: 10.1006/jmbi.2001.5140]

PubMed id

11846567

Abstract

Rad53, a yeast checkpoint protein involved in regulating the repair of DNA damage, contains two forkhead-associated domains, FHA1 and FHA2. Previous combinatorial library screening has shown that FHA1 strongly selects peptides containing a pTXXD motif. Subsequent location of this motif within the sequence of Rad9, the target protein, coupled with spectroscopic analysis has led to identification of a tight binding sequence that is likely the binding site of FHA1: (188)SLEV(pT)EADATFVQ(200). We present solution structures of FHA1 in complex with this pT-peptide and with another Rad9-derived pT-peptide that has ca 30-fold lower affinity, (148)KKMTFQ(pT)PTDPLE(160). Both complexes showed intermolecular NOEs predominantly between three peptide residues (pT, +1, and +2 residues) and five FHA1 residues (S82, R83, S85, T106, and N107). Furthermore, the following interactions were implicated on the basis of chemical shift perturbations and structural analysis: the phosphate group of the pT residue with the side-chain amide group of N86 and the guanidino group of R70, and the carboxylate group of Asp (at the +3 position) with the guanidino group of R83. The generated structures revealed a similar binding mode adopted by these two peptides, suggesting that pT and the +3 residue Asp are the major contributors to binding affinity and specificity, while +1 and +2 residues could provide additional fine-tuning. It was also shown that FHA1 does not bind to the corresponding pS-peptides or a related pY-peptide. We suggest that differentiation between pT and pS-peptides by FHA1 can be attributed to hydrophobic interactions between the methyl group of the pT residue and the aliphatic protons of R83, S85, and T106 from FHA1.

Figure 5.
Figure 5. Stereoview of 20 overlaid structures of (a) FHA1-pT2 and (b) FHA1-pT1. The C^a traces of FHA1 include residues from 28 to 157, and only the heavy atoms of residues pT through the +3 position are shown. The phosphate groups are highlighted in red.

Figure 6.
Figure 6. Charge distribution at the surface of FHA1. Positive, negative, and neutral potentials are blue, red, and white, respectively.

The above figures are reprinted by permission from Elsevier: J Mol Biol (2001, 314, 563-575) copyright 2001.