TY - JOUR
T1 - 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
AU - Ermakova, Elena
AU - Miller, Michelle C.
AU - Nesmelova, Irina V.
AU - Lopez-Merino, Lara
AU - Alvaro Berbis, Manuel
AU - Nesmelov, Yuri
AU - Tkachev, Yaroslav V.
AU - Lagartera, Laura
AU - Daragan, Vladimir A.
AU - Andre, Sabine
AU - Javier Canada, F.
AU - Jimenez-Barbero, Jesus
AU - Solis, Dolores
AU - Gabius, Hans-Joachim
AU - Mayo, Kevin H.
PY - 2013/5
Y1 - 2013/5
N2 - 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.
AB - 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.
KW - circular dichroism
KW - FRET
KW - galectin
KW - molecular dynamics
KW - NMR
U2 - 10.1093/glycob/cwt005
DO - 10.1093/glycob/cwt005
M3 - Article
C2 - 23376190
SN - 0959-6658
VL - 23
SP - 508
EP - 523
JO - Glycobiology
JF - Glycobiology
IS - 5
ER -