Format

Send to

Choose Destination
See comment in PubMed Commons below
J Biol Chem. 2015 Dec 18;290(51):30390-405. doi: 10.1074/jbc.M115.689604. Epub 2015 Oct 16.

Assembly and Molecular Architecture of the Phosphoinositide 3-Kinase p85α Homodimer.

Author information

  • 1From the Department of Molecular Pharmacology.
  • 2the Department of Bioengineering and Therapeutic Sciences, Department of Pharmaceutical Chemistry, and California Institute for Quantitative Biosciences, University of California, San Francisco, San Francisco, California 94158, and.
  • 3the Laboratory of Mass Spectrometry and Gaseous Ion Chemistry, The Rockefeller University, New York, New York 10065.
  • 4Department of Anatomy and Structural Biology, Albert Einstein College of Medicine, Bronx, New York 10461.
  • 5Department of Biochemistry, michael.brenowitz@einstein.yu.edu.
  • 6Department of Biochemistry, anne.bresnick@einstein.yu.edu.
  • 7From the Department of Molecular Pharmacology, Department of Biochemistry, jonathan.backer@einstein.yu.edu.

Abstract

Phosphoinositide 3-kinases (PI3Ks) are a family of lipid kinases that are activated by growth factor and G-protein-coupled receptors and propagate intracellular signals for growth, survival, proliferation, and metabolism. p85α, a modular protein consisting of five domains, binds and inhibits the enzymatic activity of class IA PI3K catalytic subunits. Here, we describe the structural states of the p85α dimer, based on data from in vivo and in vitro solution characterization. Our in vitro assembly and structural analyses have been enabled by the creation of cysteine-free p85α that is functionally equivalent to native p85α. Analytical ultracentrifugation studies showed that p85α undergoes rapidly reversible monomer-dimer assembly that is highly exothermic in nature. In addition to the documented SH3-PR1 dimerization interaction, we identified a second intermolecular interaction mediated by cSH2 domains at the C-terminal end of the polypeptide. We have demonstrated in vivo concentration-dependent dimerization of p85α using fluorescence fluctuation spectroscopy. Finally, we have defined solution conditions under which the protein is predominantly monomeric or dimeric, providing the basis for small angle x-ray scattering and chemical cross-linking structural analysis of the discrete dimer. These experimental data have been used for the integrative structure determination of the p85α dimer. Our study provides new insight into the structure and assembly of the p85α homodimer and suggests that this protein is a highly dynamic molecule whose conformational flexibility allows it to transiently associate with multiple binding proteins.

KEYWORDS:

analytical ultracentrifugation; molecular modeling; phosphatidylinositide 3-kinase (PI 3-kinase); phosphatidylinositol signaling; small-angle X-ray scattering (SAXS); structural model

PMID:
26475863
PMCID:
PMC4683262
DOI:
10.1074/jbc.M115.689604
[PubMed - indexed for MEDLINE]
Free PMC Article
PubMed Commons home

PubMed Commons

0 comments
How to join PubMed Commons

    Supplemental Content

    Full text links

    Icon for HighWire Icon for PubMed Central
    Loading ...
    Support Center