Study of the interaction of the Ig2 module of the fibroblast growth factor receptor, FGFR Ig2, with the fibroblast growth factor 1, FGF1, by means of NMR spectroscopy

AbstractFibroblast growth factor (FGF) receptor (FGFR) consists extracellularly of three immunoglobulin (Ig) modules (Ig1–3). Currently, there are two competing models (symmetric and asymmetric) of the FGF–FGFR–heparin complex based on crystal structures. Indirect evidence exists in support of both models. However, it is not clear which model is physiologically relevant. Our aim was to obtain direct, non-crystallographic evidence in support of them. We found by nuclear magnetic resonance that Ig2 could bind to FGF1 not only via the primary site (present in both models), but also via the secondary site (present only in the symmetric model). Thus, our data support the symmetric model

Study of structure, base-pair opening kinetics and proton exchange mechanism of the d-(AATTGCAATT) self-complementary oligodeoxynucleotide in solution.

Using proton magnetic resonance, we have investigated the structure and the base-pair opening kinetics of the d-(AATTGCAATT) self-complementary duplex. All the non-exchangeable (except H5',5") and most exchangeable proton resonances have been assigned. The structure belongs to the B family. Imino proton exchange, measured by line broadening, longitudinal relaxation and magnetization transfer from water, is catalyzed by proton acceptors. The base-pair lifetimes, obtained by extrapolation of the exchange times to infinite concentration of ammonia are 2 and 3 milliseconds for internal A.Ts and 18 ms for G.C at 15 degrees C. In the absence of added catalysts, the imino proton of the first A.T base pair exchanges faster than that of the unpaired thymidine of the duplex formed by the sequence d-(AATTGCAATTT). This gives strong evidence for intrinsic exchange catalysis. The exchange of adenine amino protons from the closed state has been observed. Hence amino proton exchange is ill-suited for the investigation of base-pair opening kinetics

From genetic to structural characterization of a new class of RNA-binding domain within the SacY/BglG family of antiterminator proteins.

SacY is the prototype of a family of regulatory proteins able to prevent transcription termination. It interacts with a 29 nucleotide RNA sequence able to fold into a stem-loop structure and partially overlapping with a terminator sequence located in the 5' leader mRNA region of the gene it controls. We show here that the N-terminal fragment of SacY, SacY(1-55), and the corresponding fragments of other members of the family have antiterminator activities with efficiency and specificity identical to those of the full-length proteins. In vitro, this activity correlates with the specific affinity of SacY(1-55) for its RNA target. UV melting experiments demonstrate that SacY(1-55) binding stabilizes the RNA target structure. The NMR solution structure of SacY(1-55) is very similar to that obtained in the crystal (van Tilbeurgh et al., 1997): the peptide is folded as a symmetrical dimer without any structural homology with other RNA-binding domains yet characterized. According to a preliminary NMR analysis of the SacY(1-55)-RNA complex, the protein dimer is not disrupted upon RNA binding and several residues implicated in RNA recognition are located at the edge of the dimer interface. This suggests a new mode of protein-RNA interaction

Crystal structure of a new RNA-binding domain from the antiterminator protein SacY of Bacillus subtilis.

SacY belongs to a family of, at present, seven bacterial transcriptional antiterminators. The RNA-binding and antitermination capacity of SacY resides in the 55 amino acids at the N-terminal [SacY(1-55)]. The crystal structure at 2 A resolution shows that SacY(1-55) forms a dimer in the crystal, in accordance with the NMR solution structure. The structure of the monomer is a four-stranded beta-sheet with a simple beta1beta2beta3beta4 topology. One side of the sheet is covered by a long surface loop and the other side forms the dimer interface. The dimer is stabilized by the orthogonal stacking of the two beta-sheets. The crystal structure is in excellent agreement with the NMR solution structure (r.m.s. distance for C alpha coordinates is 1.3 A). The structure of SacY(1-55) reveals a new RNA-binding motif