Crystallization of a human galectin-3 variant with two ordered segments in the shortened N-terminal tail

Abstract

Among members of the family of adhesion/growth-regulatory galectins, galectin-3 (Gal-3) bears a unique modular architecture. A N-terminal tail (NT) consisting of the N-terminal segment (NTS) and nine collagen-like repeats is linked to the canonical lectin domain. In contrast to bivalent proto- and tandem-repeat-type galectins, Gal-3 is monomeric in solution, capable to self-associate in the presence of bi- to multivalent ligands, and the NTS is involved in cellular compartmentalization. Since no crystallographic information on Gal-3 beyond the lectin domain is available, we used a shortened variant with NTS and repeats VII-IX. This protein crystallized as tetramers with contacts between the lectin domains. The region from Tyr101 (in repeat IX) to Leu114 (in the CRD) formed a hairpin. The NTS extends the canonical β-sheet of F1-F5 strands with two new β-strands on the F face. Together, crystallographic and SAXS data reveal a mode of intramolecular structure building involving the highly flexible Gal-3’s NT.

Galectins‐1 and ‐3 in Human Intervertebral Disc Degeneration: Non‐Uniform Distribution Profiles and Activation of Disease Markers Involving NF‐κB by Galectin‐1

“…Immunopositivity for Gal‐3 was detected in the NP, and also in the other compartments. Its presence within the cells and in the matrix supports the concept of site‐specific activities, for example via its anti‐apoptotic intracellular and glycan‐dependent extracellular mechanisms involving Gal‐3‐mediated counterreceptor aggregation . A respective impact on chondrocyte survival was inferred by localization studies considering hypertrophy and in a knock‐out model, as also suggested for Gal‐3 in osteoarthritis .…”

“…Its presence within the cells and in the matrix supports the concept of site-specific activities, for example via its anti-apoptotic intracellular and glycan-dependent extracellular mechanisms involving Gal-3-mediated counterreceptor aggregation. 42 A respective impact on chondrocyte survival was inferred by localization studies considering hypertrophy and in a knock-out model, as also suggested for Gal-3 in osteoarthritis. 7,43,44 In rat NP cells, Gal-3 knock-down led to increased susceptibility to FasL-induced cell death, 28 and a functional cooperation between tumor necrosis factor-α and Gal-3 on IL-1β, IL-6, and CCL2 expression had been reported.…”

Pro4 prolyl peptide bond isomerization in human galectin-7 modulates the monomer-dimer equilibrum to affect function

“…For example, the N-terminus can move between a core-associated and a more solvent-exposed structure. Since shuttling between cellular compartments, as well as export, may involve this region as indicated with Gal-3 and its structural organization at this site [78,79], and N-terminal contact has been documented for Gal-1 around L11 in Ras-dependent growth regulation [80], tipping the balance toward one conformer or another here could be physiologically relevant, even providing a possible explanation for different intracellular routing of a galectin. Of note, the detected alterations go beyond the conformational repositioning at P4, as it affects the lectin more globally.…”

A Brief History of Charcot-Leyden Crystal Protein/Galectin-10 Research

“…Even though many crystal structures of the Gal-3 CRD have been reported [ 47 , 48 , 49 , 50 ], its N-terminal tail is highly flexible and interacts transiently with the F-face of the CRD [ 51 ], a dynamic situation that precludes crystallization of the full-length lectin. Recently, an interesting crystal structure of Gal-3 was published showing that a short peptide from Gal-3 N-terminal tail can extend the CRD F-face β-sheet [ 52 ].…”