title: PWWP module of human hepatoma-derived growth factor forms a domain-swapped dimer with much higher affinity for heparin.
abstract: Hepatoma-derived growth factor (hHDGF)-related proteins (HRPs) comprise a new growth factor family sharing a highly conserved and ordered N-terminal PWWP module (residues 1-100, previously referred to as a HATH domain) and a variable disordered C-terminal domain. We have shown that the PWWP module is responsible for heparin binding and have solved its structure in solution. Here, we show that under physiological conditions, both the PWWP module and hHDGF can form dimers. Surface plasmon resonance (SPR) studies revealed that the PWWP dimer binds to heparin with affinity that is two orders of magnitude higher (K(d)=13 nM) than that of the monomeric PWWP module (K(d)=1.2 microM). The monomer-dimer equilibrium properties and NMR structural data together suggest that the PWWP dimer is formed through a domain-swapping mechanism. The domain-swapped PWWP dimer structures were calculated on the basis of the NMR data. The results show that the two PWWP protomers exchange their N-terminal hairpin to form a domain-swapped dimer. The two monomers in a dimer are linked by the long flexible L2 loops, a feature supported by NMR relaxation data for the monomer and dimer. The enhanced heparin-binding affinity of the dimer can be rationalized in the framework of the dimer structure.
authors.affiliation: Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan, R.O.C.
authors.forename: Shih-Che
authors.initials: SC
authors.lastname: Sue
authors.forename: Wei-Tin
authors.initials: WT
authors.lastname: Lee
authors.forename: Shi-Chi
authors.initials: SC
authors.lastname: Tien
authors.forename: Shao-Chen
authors.initials: SC
authors.lastname: Lee
authors.forename: Jiun-Guo
authors.initials: JG
authors.lastname: Yu
authors.forename: Wen-Jin
authors.initials: WJ
authors.lastname: Wu
authors.forename: Wen-guey
authors.initials: WG
authors.lastname: Wu
authors.forename: Tai-huang
authors.initials: TH
authors.lastname: Huang
mesh_terms: D001665:Binding Sites; D004247:DNA; D019281:Dimerization; D006493:Heparin / Q000378:metabolism*; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins / Q000737:chemistry* / Q000378:metabolism; D008958:Models, Molecular; D011485:Protein Binding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary
chemical_list: D036341:Intercellular Signaling Peptides and Proteins; C051610:hepatoma-derived growth factor; D006493:Heparin; D004247:DNA