title: Supertertiary structure of the synaptic MAGuK scaffold proteins is conserved.
abstract: Scaffold proteins form a framework to organize signal transduction by binding multiple partners within a signaling pathway. This shapes the output of signal responses as well as providing specificity and localization. The Membrane Associated Guanylate Kinases (MAGuKs) are scaffold proteins at cellular junctions that localize cell surface receptors and link them to downstream signaling enzymes. Scaffold proteins often contain protein-binding domains that are connected in series by disordered linkers. The tertiary structure of the folded domains is well understood, but describing the dynamic inter-domain interactions (the superteritary structure) of such multidomain proteins remains a challenge to structural biology. We used 65 distance restraints from single-molecule fluorescence resonance energy transfer (smFRET) to describe the superteritary structure of the canonical MAGuK scaffold protein PSD-95. By combining multiple fluorescence techniques, the conformational dynamics of PSD-95 could be characterized across the biologically relevant timescales for protein domain motions. Relying only on a qualitative interpretation of FRET data, we were able to distinguish stable interdomain interactions from freely orienting domains. This revealed that the five domains in PSD-95 partitioned into two independent supramodules: PDZ1-PDZ2 and PDZ3-SH3-GuK. We used our smFRET data for hybrid structural refinement to model the PDZ3-SH3-GuK supramodule and include explicit dye simulations to provide complete characterization of potential uncertainties inherent to quantitative interpretation of FRET as distance. Comparative structural analysis of synaptic MAGuK homologues showed a conservation of this supertertiary structure. Our approach represents a general solution to describing the supertertiary structure of multidomain proteins.
authors.affiliation: Departments of Pharmacological Sciences, Stony Brook University, Stony Brook, NY 11794, USA.
authors.forename: James J
authors.initials: JJ
authors.lastname: McCann
authors.forename: Liqiang
authors.initials: L
authors.lastname: Zheng
authors.forename: Daniel
authors.initials: D
authors.lastname: Rohrbeck
authors.forename: Suren
authors.initials: S
authors.lastname: Felekyan
authors.forename: Ralf
authors.initials: R
authors.lastname: Kühnemuth
authors.forename: R Bryan
authors.initials: RB
authors.lastname: Sutton
authors.forename: Claus A M
authors.initials: CA
authors.lastname: Seidel
authors.forename: Mark E
authors.initials: ME
authors.lastname: Bowen
mesh_terms: D000818:Animals; D000076122:Disks Large Homolog 4 Protein; D031541:Fluorescence Resonance Energy Transfer / Q000379:methods; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000737:chemistry*; D008565:Membrane Proteins / Q000737:chemistry*; D020836:Protein Structure, Quaternary; D017434:Protein Structure, Tertiary
chemical_list: C501444:DLG4 protein, human; D000076122:Disks Large Homolog 4 Protein; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins