Abstract
Galectin-3 (Gal-3) is a β-galactosidase-binding protein involved in various biological processes, including neuronal growth and adhesion. The pairing of Gal-3 with ganglioside GM1's pentasaccharide chain at the outer leaflet of the plasma membrane, which triggers downstream cell-signaling cascades, seems to be involved in these processes. A crucial feature of Gal-3 is its ability to form oligomers and supramolecular assemblies that connect various carbohydrate-decorated molecules. Although we know the atomistic structure of Gal-3 bound to small carbohydrate ligands, it remains unclear how Gal-3 binds GM1 in a membrane. Furthermore, the influence of this interaction on Gal-3's structure and oligomeric assembly has to be elucidated. In this study, we used X-ray reflectivity (XR) from a model membrane to determine the structure and surface coverage of Gal-3 bound to a membrane containing GM1. We observed that the carbohydrate recognition domain interacts with GM1's pentasaccharide, while the N-terminal domain is pointed away from the membrane, likely to facilitate protein-protein interactions. In a membrane containing 20 mol % GM1, Gal-3 covered ∼50% of the membrane surface with one Gal-3 molecule bound per 2130 Å2. We used molecular dynamics simulations and Voronoi tessellation algorithms to build an atomistic model of membrane-bound Gal-3, which is supported by the XR results. Overall, this work provides structural information describing how Gal-3 can bind GM1's pentasaccharide chain, a prerequisite for triggering regulatory processes in neuronal growth and adhesion.
| Original language | English |
|---|---|
| Pages (from-to) | 1926-1937 |
| Number of pages | 12 |
| Journal | Biophysical Journal |
| Volume | 122 |
| Issue number | 11 |
| DOIs | |
| State | Published - Jun 6 2023 |
| Externally published | Yes |
Funding
The authors would like to express sincere appreciation for the careful evaluation and feedback given by Prof. Herbert Kaltner, Dr. Joachim Manning, and Dr. Anna-Kristin Ludwig on this work. NSF provided support for J.M. to contribute to this project through their Independent Research and Development program. Any opinion, findings, conclusions, or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation. D.B. was funded by the UCCS Undergraduate Research Academy and a UCCS College of Letters, Arts, and Sciences Research Assistant Scholarship. Y.W. was funded by the BRAiN Undergraduate Research Program ( NIH award R25NS080685 ). XR data were collected at NSF ’s ChemMatCARS, which is supported by the Divisions of Chemistry (CHE) and Materials Research (DMR) , National Science Foundation , under grant number NSF/CHE-1834750 . The authors are grateful to beamline scientist Dr. Wei Bu for support during XR data collection.