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J Am Soc Mass Spectrom. 2017 Jan;28(1):96-109. doi: 10.1007/s13361-016-1496-8. Epub 2016 Sep 23.

Gas-Phase Analysis of the Complex of Fibroblast GrowthFactor 1 with Heparan Sulfate: A Traveling Wave Ion Mobility Spectrometry (TWIMS) and Molecular Modeling Study.

Author information

1
Department of Chemistry, University of Georgia, Athens, GA, 30602, USA.
2
Complex Carbohydrate Research Center, University of Georgia, Athens, GA, 30602, USA.
3
Eshelman School of Pharmacy, Division of Chemical Biology and Medicinal Chemistry, University of North Carolina, Chapel Hill, NC, USA.
4
Center for Biotechnology and Interdisciplinary Studies, Department of Chemistry and Chemical Biology, Rensselaer Polytechnic Institute, Troy, NY, USA.
5
Department of Chemistry, University of Georgia, Athens, GA, 30602, USA. jamster@uga.edu.

Abstract

Fibroblast growth factors (FGFs) regulate several cellular developmental processes by interacting with cell surface heparan proteoglycans and transmembrane cell surface receptors (FGFR). The interaction of FGF with heparan sulfate (HS) is known to induce protein oligomerization, increase the affinity of FGF towards its receptor FGFR, promoting the formation of the HS-FGF-FGFR signaling complex. Although the role of HS in the signaling pathways is well recognized, the details of FGF oligomerization and formation of the ternary signaling complex are still not clear, with several conflicting models proposed in literature. Here, we examine the effect of size and sulfation pattern of HS upon FGF1 oligomerization, binding stoichiometry and conformational stability, through a combination of ion mobility (IM) and theoretical modeling approaches. Ion mobility-mass spectrometry (IMMS) of FGF1 in the presence of several HS fragments ranging from tetrasaccharide (dp4) to dodecasaccharide (dp12) in length was performed. A comparison of the binding stoichiometry of variably sulfated dp4 HS to FGF1 confirmed the significance of the previously known high-affinity binding motif in FGF1 dimerization, and demonstrated that certain tetrasaccharide-length fragments are also capable of inducing dimerization of FGF1. The degree of oligomerization was found to increase in the presence of dp12 HS, and a general lack of specificity for longer HS was observed. Additionally, collision cross-sections (CCSs) of several FGF1-HS complexes were calculated, and were found to be in close agreement with experimental results. Based on the (CCSs) a number of plausible binding modes of 2:1 and 3:1 FGF1-HS are proposed. Graphical Abstract ᅟ.

KEYWORDS:

Fibroblast growth factor; Glycosaminoglycan; Ion mobility; Native mass spectrometry; TWIMS

PMID:
27663556
PMCID:
PMC5177502
DOI:
10.1007/s13361-016-1496-8
[Indexed for MEDLINE]
Free PMC Article

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