PDBsum entry: 1q1u

Hormone/growth factor

PDB id: 1q1u

Contents

Protein chain

138 a.a. *

Ligands

SO4 ×4

Waters ×36

* Residue conservation analysis

PDB id:

1q1u

Name:

Hormone/growth factor

Title:

Crystal structure of human fhf1b (fgf12b)

Structure:

Fibrobast growth factor homologous factor 1. Chain: a. Fragment: residues 1-144. Synonym: fgf-12. Fgf12b. Fibroblast growth factor 12 isoform 2. Myocyte-activating factor. Fgf12 protein. Engineered: yes. Mutation: yes

Source:

Homo sapiens. Human. Organism_taxid: 9606. Expressed in: escherichia coli bl21. Expression_system_taxid: 511693. Other_details: t7 promoter driven expression

Resolution:

1.70Å R-factor: 0.223 R-free: 0.240

Authors:

S.K.Olsen,M.Garbi,N.Zampieri,A.V.Eliseenkova,D.M.Ornitz, M.Goldfarb,M.Mohammadi

Key ref:

S.K.Olsen et al. (2003). Fibroblast growth factor (FGF) homologous factors share structural but not functional homology with FGFs. J Biol Chem, 278, 34226-34236. PubMed id: 12815063 DOI: 10.1074/jbc.M303183200

Date:

22-Jul-03 Release date: 05-Aug-03

Protein chain

P61328  (FGF12_HUMAN) -  Fibroblast growth factor 12

Seq: 243 a.a.

Struc: 138 a.a.

 Gene Ontology (GO) functional annotation 

• Biochemical function: growth factor activity (1 term)

DOI no: 10.1074/jbc.M303183200

J Biol Chem 278:34226-34236 (2003)

PubMed id: 12815063

Fibroblast growth factor (FGF) homologous factors share structural but not functional homology with FGFs.

S.K.Olsen, M.Garbi, N.Zampieri, A.V.Eliseenkova, D.M.Ornitz, M.Goldfarb, M.Mohammadi.

ABSTRACT

Fibroblast growth factors (FGFs) interact with heparan sulfate glycosaminoglycans and the extracellular domains of FGF cell surface receptors (FGFRs) to trigger receptor activation and biological responses. FGF homologous factors (FHF1-FHF4; also known as FGF11-FGF14) are related to FGFs by substantial sequence homology, yet their only documented interactions are with an intracellular kinase scaffold protein, islet brain-2 (IB2) and with voltage-gated sodium channels. In this report, we show that recombinant FHFs can bind heparin with high affinity like classical FGFs yet fail to activate any of the seven principal FGFRs. Instead, we demonstrate that FHFs bind IB2 directly, furthering the contention that FHFs and FGFs elicit their biological effects by binding to different protein partners. To understand the molecular basis for this differential target binding specificity, we elucidated the crystal structure of FHF1b to 1.7-A resolution. The FHF1b core domain assumes a beta-trefoil fold consisting of 12 antiparallel beta strands (beta 1 through beta 12). The FHF1b beta-trefoil core is remarkably similar to that of classical FGFs and exhibits an FGF-characteristic heparin-binding surface as attested to by the number of bound sulfate ions. Using molecular modeling and structure-based mutational analysis, we identified two surface residues, Arg52 in the beta 4-beta 5 loop and Val95 in the beta 9 strand of FHF1b that are required for the interaction of FHF1b with IB2. These two residues are unique to FHFs, and mutations of the corresponding residues of FGF1 to Arg and Val diminish the capacity of FGF1 to activate FGFRs, suggesting that these two FHF residues contribute to the inability of FHFs to activate FGFRs. Hence, FHFs and FGFs bear striking structural similarity but have diverged to direct related surfaces toward interaction with distinct protein targets.

Selected figure(s)

Figure 3.
FIG. 3. FHF1b binds IB2 directly. Recombinant FHFs were mixed with partially purified mIB2[226-421] at a 1:3 molar ratio and chromatographed through a Superdex 75 gel filtration column. Fractions were analyzed by SDS-PAGE followed by silver staining. A, FHF1b only; B, FHF1b + mIB2[226-421]; C, FHF4b only; D, FHF4b + mIB2[226-421]; E, FHF1b[1-142]. Wild-type FHFs alone elute slowly, whereas they co-elute rapidly when complexed with mIB2[226-421].

Figure 5.
FIG. 5. Comparison of FHF1b versus FGF structure. A, stereo view of FHF1b-FGF9 overlay. The C trace of FGF9 -trefoil (blue) was superimposed onto the C trace of the FHF1b -trefoil (orange). The N and C termini are labeled NT and CT, respectively. The [8]- [9] turn of the ligands (discussed under "Results") are marked by an arrowhead. This figure was created using the program MolScript (59). B, stereo view of the electron density map of the FHF1b heparin-binding site. The 2F[o]-F[c] electron density map (contoured at 1.2 ) is shown as white (FHF1b) and cyan (sulfate ions) wire mesh. The FHF1b -trefoil core is shown as a ribbon diagram, and residues that interact with the sulfate ions are rendered as sticks. Ordered sulfate ions are also rendered as sticks. This figure was created using the program PyMOL (56).

The above figures are reprinted by permission from the ASBMB: J Biol Chem (2003, 278, 34226-34236) copyright 2003.

Figures were selected by an automated process.