UV Resonance Raman Determination of Ligand-Induced Thermal Stabilization of Galectin-1

SANTIAGO DI LELLA; GABRIEL A. RABINOVICH; ROSA MARIA SUSANA ALVAREZ

Salta

Congreso; XXXIX Anual Meeting of the Argentinean Biophysical Society- 3rd Latin American Protein Society Meeting; 2010

Sociedad Argentina de Biofísica

Many factors can modify the balance that determines the protein stability between the native and the unfolded states. For example, non-covalent interactions of proteins with their ligands often increase the protein thermal stability. Since proteins are designed to have ligands bind preferentially to their native state, the increased ligand bound protein thermal stability, is a straightforward example of Le Chatelierfs principle. In this work, we studied the dependence of protein thermal stability upon ligand binding using Galectin-1 (Gal-1), a b-galactoside-binding protein composed of 134 aminoacids. Gal-1 is involved in cell growth regulation and differentiation, as well as in the modulation of innate and adaptive immune responses1,2. Protein conformation consists of a tightly folded conserved ƒÀ-sandwich structure formed by two antiparallel ƒÀ sheets of five (F1-F5) and six (S1-S6) ƒÀ-strands. Gal-1 binds its carbohydrate ligands within the carbohydrate recognition domain. The main interactions are hydrophobic and occur with an extensive hydrogen-bond network, involving specifically his44, asp46, arg48, asp61, trp68, glu71 and arg73. In order to analyze structural changes occurring upon binding, and thermal denaturation of Gal-1 and the complex, we used UV resonance Raman spectroscopy with excitation within the amide ƒÎ¨ƒÎ* transition, which gives significant information on protein secondary structure.  1. Rabinovich G. Br J Cancer, 92, 1188-1192 (2005).  2. Rabinovich G, Toscano M, Jackson D, Vasta G, Curr Opin Struct Biol 17, 513-520 (2007).