title: Intrinsic disorder and coiled-coil formation in prostate apoptosis response factor 4.
abstract: Prostate apoptosis response factor-4 (Par-4) is an ubiquitously expressed pro-apoptotic and tumour suppressive protein that can both activate cell-death mechanisms and inhibit pro-survival factors. Par-4 contains a highly conserved coiled-coil region that serves as the primary recognition domain for a large number of binding partners. Par-4 is also tightly regulated by the aforementioned binding partners and by post-translational modifications. Biophysical data obtained in the present study indicate that Par-4 primarily comprises an intrinsically disordered protein. Bioinformatic analysis of the highly conserved Par-4 reveals low sequence complexity and enrichment in polar and charged amino acids. The high proteolytic susceptibility and an increased hydrodynamic radius are consistent with a largely extended structure in solution. Spectroscopic measurements using CD and NMR also reveal characteristic features of intrinsic disorder. Under physiological conditions, the data obtained show that Par-4 self-associates via the C-terminal domain, forming a coiled-coil. Interruption of self-association by urea also resulted in loss of secondary structure. These results are consistent with the stabilization of the coiled-coil motif through an intramolecular association.
authors.affiliation: Centre for Structural Biology, Institute of Fundamental Sciences, Massey University, Palmerston North, New Zealand. d.s.libich@massey.ac.nz
authors.forename: David S
authors.initials: DS
authors.lastname: Libich
authors.forename: Martin
authors.initials: M
authors.lastname: Schwalbe
authors.forename: Sachin
authors.initials: S
authors.lastname: Kate
authors.forename: Hariprasad
authors.initials: H
authors.lastname: Venugopal
authors.forename: Jolyon K
authors.initials: JK
authors.lastname: Claridge
authors.forename: Patrick J B
authors.initials: PJ
authors.lastname: Edwards
authors.forename: Kaushik
authors.initials: K
authors.lastname: Dutta
authors.forename: Steven M
authors.initials: SM
authors.lastname: Pascal
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002942:Circular Dichroism; D017124:Conserved Sequence; D006801:Humans; D008969:Molecular Sequence Data; D019906:Nuclear Magnetic Resonance, Biomolecular; D017433:Protein Structure, Secondary; D051381:Rats; D018179:Receptors, Thrombin / Q000737:chemistry* / Q000235:genetics; D016415:Sequence Alignment
chemical_list: D018179:Receptors, Thrombin; C112908:protease-activated receptor 4