title: Lactose binding to human galectin-7 (p53-induced gene 1) induces long-range effects through the protein resulting in increased dimer stability and evidence for positive cooperativity.
abstract: The product of p53-induced gene 1 is a member of the galectin family, i.e., galectin-7 (Gal-7). To move beyond structural data by X-ray diffraction, we initiated the study of the lectin by nuclear magnetic resonance (NMR) and circular dichroism spectroscopies, and molecular dynamics (MD) simulations. In concert, our results indicate that lactose binding to human Gal-7 induces long-range effects (minor conformational shifts and changes in structural dynamics) throughout the protein that result in stabilization of the dimer state, with evidence for positive cooperativity. Monte Carlo fits of (15)N-Gal-7 HSQC titrations with lactose using a two-site model yield K1 = 0.9 ± 0.6 × 10(3) M(-1) and K2 = 3.4 ± 0.8 × 10(3) M(-1). Ligand binding-induced stabilization of the Gal-7 dimer was supported by several lines of evidence: MD-based calculations of interaction energies between ligand-loaded and ligand-free states, gel filtration data and hetero-FRET spectroscopy that indicate a highly reduced tendency for dimer dissociation in the presence of lactose, CD-based thermal denaturation showing that the transition temperature of the lectin is significantly increased in the presence of lactose, and saturation transfer difference (STD) NMR using a molecular probe of the monomer state whose presence is diminished in the presence of lactose. MD simulations with the half-loaded ligand-bound state also provided insight into how allosteric signaling may occur. Overall, our results reveal long-range effects on Gal-7 structure and dynamics, which factor into entropic contributions to ligand binding and allow further comparisons with other members of the galectin family.
authors: Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, 6-155 Jackson Hall, 321 Church Street, Minneapolis, MN 55455, USA.
authors: Elena
authors: E
authors: Ermakova
authors: Michelle C
authors: MC
authors: Miller
authors: Irina V
authors: IV
authors: Nesmelova
authors: Lara
authors: L
authors: López-Merino
authors: Manuel Alvaro
authors: MA
authors: Berbís
authors: Yuri
authors: Y
authors: Nesmelov
authors: Yaroslav V
authors: YV
authors: Tkachev
authors: Laura
authors: L
authors: Lagartera
authors: Vladimir A
authors: VA
authors: Daragan
authors: Sabine
authors: S
authors: André
authors: F Javier
authors: FJ
authors: Cañada
authors: Jesús
authors: J
authors: Jiménez-Barbero
authors: Dolores
authors: D
authors: Solís
authors: Hans-Joachim
authors: HJ
authors: Gabius
authors: Kevin H
authors: KH
authors: Mayo
mesh_terms: D000494:Allosteric Regulation; D000595:Amino Acid Sequence; D037161:Galectins / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D007785:Lactose / Q000378:metabolism*; D056004:Molecular Dynamics Simulation; D008969:Molecular Sequence Data; D011485:Protein Binding; D011489:Protein Denaturation; D055503:Protein Multimerization; D055550:Protein Stability
chemical_list: D037161:Galectins; C092525:LGALS7 protein, human; D007785:Lactose
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