title: Structural differences between the SH3-HOOK-GuK domains of SAP90/PSD-95 and SAP97.
abstract: The SH3-HOOK-GUK domains of the postsynaptic scaffolding proteins SAP90/PSD-95 and SAP97 are established targets of synaptic plasticity processes in the brain. A crucial molecular mechanism involved is the transition of this domain to different conformational states. We purified the SH3-HOOK-GUK domain of both proteins to examine variations in protein conformation and stability. As monitored by circular dichroism and differential scanning calorimetry, SAP97 (T(m)=64 degrees C) is significantly more thermal stable than SAP90/PSD-95 (T(m)=52 degrees C) and follows a bimodal phase transition. GdmCl-induced equilibrium unfolding of both proteins follows the two-state transitions and thus does not involve the accumulation of stable intermediate state(s). Equilibrium unfolding of SAP97 is highly cooperative from a native state to an unfolded state. In contrast, SAP90/PSD-95 follows a non-cooperative transition from native to unfolded states. A highly cooperative unfolding reaction in case of SAP97 indicates that the protein existed initially as a compact, well-folded structure, while the gradual, non-cooperative melting reaction in case of SAP90/PSD-95 indicates that the protein is in comparison more flexible.
authors.affiliation: Centre for Cellular and Molecular Biology, Council for Scientific and Industrial Research (CSIR), Hyderabad-500007, India.
authors.forename: Rama Ramesh
authors.initials: RR
authors.lastname: Vandanapu
authors.forename: Aditya Kumar
authors.initials: AK
authors.lastname: Singh
authors.forename: Marina
authors.initials: M
authors.lastname: Mikhaylova
authors.forename: Pasham Parameshwar
authors.initials: PP
authors.lastname: Reddy
authors.forename: Michael R
authors.initials: MR
authors.lastname: Kreutz
authors.forename: Yogendra
authors.initials: Y
authors.lastname: Sharma
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D002942:Circular Dichroism; D000076122:Disks Large Homolog 4 Protein; D057927:Hydrophobic and Hydrophilic Interactions; D047908:Intracellular Signaling Peptides and Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D008565:Membrane Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D011487:Protein Conformation; D017510:Protein Folding; D055550:Protein Stability; D017434:Protein Structure, Tertiary; D051381:Rats; D016415:Sequence Alignment; D013050:Spectrometry, Fluorescence; D013696:Temperature; D018909:src Homology Domains
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D000076122:Disks Large Homolog 4 Protein; C501119:Dlg1 protein, rat; C501449:Dlg4 protein, rat; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins