title: Rational design of cyclic peptides to disrupt TGF-Β/SMAD7 signaling in heterotopic ossification.
abstract: The human TGF-β/SMAD7 signaling has been recognized as an attractive target of heterotopic ossification (HO). Here, we report a successful rational design of cyclic peptides to disrupt the signaling pathway by targeting TGF-β-receptor complex. The intermolecular interaction between TGF-β and its cognate receptor is characterized in detail using molecular dynamics simulation, binding energetic analysis, and alanine scanning. With the computational analysis a binding loop of receptor protein is identified that plays an essential role in the peptide-mediated TGF-β-receptor interaction. Subsequently, the loop is stripped from the protein context to generate a linear peptide segment, which possesses considerable flexibility and intrinsic disorder, and thus would incur a large entropy penalty upon binding to TGF-β. In order to minimize the unfavorable entropic effect, the linear peptide is cyclized by adding a disulfide bond between the N- and C-terminal cysteine residues of the peptide, resulting in a cyclic peptide. In vitro fluorescence anisotropy assays substantiate that the cyclic peptide can bind tightly to TGF-β with determined Kdvalue of 54μM. We also demonstrated that structural optimization can further improve the peptide affinity by site-directed mutagenesis of selected residues based on the computationally modeled complex structure of TGF-β with the cyclic peptide.
authors.affiliation: Department of Orthopedics, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai 200233, China.
authors.forename: Biao
authors.initials: B
authors.lastname: Zhong
authors.affiliation: Department of Orthopedics, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai 200233, China.
authors.forename: Chi
authors.initials: C
authors.lastname: Zhang
authors.affiliation: Department of Orthopedics, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai 200233, China.
authors.forename: Shang
authors.initials: S
authors.lastname: Guo
authors.affiliation: Department of Orthopedics, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai 200233, China. Electronic address: zhangcq@sjtu.edu.cn.
authors.forename: Changqing
authors.initials: C
authors.lastname: Zhang
mesh_terms: D000595:Amino Acid Sequence; D015195:Drug Design; D006801:Humans; D056004:Molecular Dynamics Simulation; D009999:Ossification, Heterotopic / Q000378:metabolism*; D010456:Peptides, Cyclic / Q000737:chemistry / Q000494:pharmacology*; D055503:Protein Multimerization; D017433:Protein Structure, Secondary; D015398:Signal Transduction / Q000187:drug effects*; D051906:Smad7 Protein / Q000737:chemistry / Q000378:metabolism*; D013816:Thermodynamics; D016212:Transforming Growth Factor beta / Q000737:chemistry / Q000378:metabolism*
chemical_list: D010456:Peptides, Cyclic; D051906:Smad7 Protein; D016212:Transforming Growth Factor beta
keywords: Cyclic peptide; Heterotopic ossification; Molecular modeling; TGF-β/SMAD7 signaling