Carbohydrate chain of ganglioside GM1 as a ligand: identification of the binding strategies of three 15 mer peptides and their divergence from the binding modes of growth-regulatory galectin-1 and cholera toxin.
The branched pentasaccharide chain of ganglioside GM1 is a prominent cell surface ligand, for example, for cholera toxin or tumor growth-regulatory homodimeric galectins. This activity profile via protein recognition prompted us to examine the binding properties of peptides with this specificity. Our study provides insights into the mechanism of molecular interaction of this thus far unexplored size limit of the protein part. We used three pentadecapeptides in a combined approach of mass spectrometry, NMR spectroscopy and molecular modelling to analyze the ligand binding in solution. Availability of charged and hydrophobic functionalities affected the intramolecular flexibility of the peptides differently. Backfolding led to restrictions in two cases; the flexibility was not reduced significantly by association of the ligand in its energetically privileged conformations. Major contributions to the interaction energy arise from the sialic acid moiety contacting Arg/Lys residues and the N-terminal charge. Considerable involvement of stacking between the monovalent ligand and aromatic rings could not be detected. This carbohydrate binding strategy is similar to how an adenoviral fiber knob targets sialylated glycans. Rational manipulation for an affinity enhancement can now be directed to reduce the flexibility, exploit the potential for stacking and acquire the cross-linking capacity of the natural lectins by peptide attachment to a suitable scaffold.
Siebert
Hans-Christian
HC
Institut für Physiologische Chemie, Tierärztliche Fakultät, Ludwig-Maximilians-Universität München, Veterinärstrasse 13, 80539 München, Germany. hcsiebert@lmu.de
Born
Karin
K
André
Sabine
S
Frank
Martin
M
Kaltner
Herbert
H
von der Lieth
Claus-Wilhelm
CW
Heck
Albert J R
AJ
Jiménez-Barbero
Jesús
J
Kopitz
Jürgen
J
Gabius
Hans-Joachim
HJ
D000595:Amino Acid Sequence; D002772:Cholera Toxin / Q000737:chemistry*; D005677:G(M1) Ganglioside / Q000737:chemistry*; D037483:Galectin 1 / Q000737:chemistry*; D008024:Ligands; D008432:Mathematical Computing; D008958:Models, Molecular; D008969:Molecular Sequence Data; D019158:N-Acetylneuraminic Acid / Q000737:chemistry; D019906:Nuclear Magnetic Resonance, Biomolecular; D010455:Peptides / Q000737:chemistry*; D011487:Protein Conformation; D017510:Protein Folding
D037483:Galectin 1; D008024:Ligands; D010455:Peptides; D005677:G(M1) Ganglioside; D002772:Cholera Toxin; D019158:N-Acetylneuraminic Acid