| Abstract: | In this study, we examined the local dynamics of acidic fibroblast growth factor (FGF‐1) as well as the binding sites of various polyanions including poly‐sulfates (heparin and low MW heparin) and poly‐phosphates (phytic acid and ATP) using hydrogen‐deuterium exchange mass spectrometry (HX‐MS). For local dynamics, results are analyzed at the peptide level as well as in terms of buried amides employing crystallographic B‐factors and compared with a residue level heat map generated from HX‐MS results. Results show that strand 4 and 5 and the turn between them to be the most flexible regions as was previously seen by NMR. On the other hand, the C‐terminal strands 8, 9, and 10 appear to be more rigid which is also consistent with crystallographic B‐factors as well as local dynamics studies conducted by NMR. Crystal structures of FGF‐1 in complex with heparin have shown that heparin binds to N‐terminal Asn18 and to C‐terminal Lys105, Tryp107, Lys112, Lys113, Arg119, Pro121, Arg122, Gln127, and Lys128 indicating electrostatic forces as dominant interactions. Heparin binding as determined by HX‐MS is consistent with crystallography data. Previous studies have also shown that other polyanions including low MW heparin, phytic acid and ATP dramatically increase the thermal stability of FGF‐1. Using HX‐MS, we find other poly anions tested bind in a similar manner to heparin, primarily targeting the turns in the lysine rich C‐terminal region of FGF‐1 along with two distinct N‐terminal regions that contains lysines and arginines/histidines. This confirms the interactions between FGF‐1 and polyanions are primary directed by electrostatics. |
