NMR solution studies of hamster galectin-3 and electron microscopic visualization of surface-adsorbed complexes: evidence for interactions between the N- and C-terminal domains

Biochemistry. 2001 Apr 17;40(15):4859-66. doi: 10.1021/bi002907f.

Abstract

Galectin-3, a beta-galactoside binding protein, contains a C-terminal carbohydrate recognition domain (CRD) and an N-terminal domain that includes several repeats of a proline-tyrosine-glycine-rich motif. Earlier work based on a crystal structure of human galectin-3 CRD, and modeling and mutagenesis studies of the closely homologous hamster galectin-3, suggested that N-terminal tail residues immediately preceding the CRD might interfere with the canonical subunit interaction site of dimeric galectin-1 and -2, explaining the monomeric status of galectin-3 in solution. Here we describe high-resolution NMR studies of hamster galectin-3 (residues 1--245) and several of its fragments. The results indicate that the recombinant N-terminal fragment Delta 126--245 (residues 1--125) is an unfolded, extended structure. However, in the intact galectin-3 and fragment Delta 1--93 (residues 94--245), N-terminal domain residues lying between positions 94 and 113 have significantly reduced mobility values compared with those expected for bulk N-terminal tail residues, consistent with an interaction of this segment with the CRD domain. In contrast to the monomeric status of galectin-3 (and fragment Delta 1--93) in solution, electron microscopy of negatively stained and rotary shadowed samples of hamster galectin-3 as well as the CRD fragment Delta 1--103 (residues 104--245) show the presence of a significant proportion (up to 30%) of oligomers. Similar imaging of the N-terminal tail fragment Delta 126--245 reveals the presence of fibrils formed by intermolecular interactions between extended polypeptide subunits. Oligomerization of substratum-adsorbed galectin-3, through N- and C-terminal domain interactions, could be relevant to the positive cooperativity observed in binding of the lectin to immobilized multiglycosylated proteins such as laminin.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adsorption
  • Amino Acid Motifs
  • Amino Acid Sequence
  • Animals
  • Antigens, Differentiation / chemistry*
  • Antigens, Differentiation / genetics
  • Antigens, Differentiation / ultrastructure*
  • Carbohydrates / chemistry
  • Cricetinae
  • Galectin 3
  • Macromolecular Substances
  • Microscopy, Electron
  • Molecular Sequence Data
  • Nuclear Magnetic Resonance, Biomolecular
  • Protein Structure, Tertiary / genetics
  • Recombinant Proteins / chemistry
  • Recombinant Proteins / ultrastructure
  • Repetitive Sequences, Amino Acid
  • Solutions

Substances

  • Antigens, Differentiation
  • Carbohydrates
  • Galectin 3
  • Macromolecular Substances
  • Recombinant Proteins
  • Solutions