Solution structure and backbone dynamics of the functional cytoplasmic subdomain of human ephrin B2, a cell-surface ligand with bidirectional signaling properties.
The cytoplasmic domain of B ephrins plays a central role in bidirectional signal transduction processes controlling pattern formation and morphogenesis, such as axon guidance, cell migration, segmentation, and angiogensis. In particular, the extremely conserved last 33-residue cytoplasmic subdomain was shown to bind to both a PDZ domain for one signaling pathway [Lu et al. (2001) Cell 105, 69-79] and an SH2 domain from an alternative signaling network [Cowan and Henkemeyer (2001) Nature 413, 174-179]. To date, no structural information is available for the cytoplasmic domain of ephrin B proteins. We report here a detailed NMR study on the structural and dynamic properties of the cytoplasmic domain of human ephrin B2. Our results reveal the following: (1) the N-terminal region of the cytoplasmic domain from residues 253 to 300 lacks the ability for structure formation and is particularly prone to aggregation; and (2) the C-terminal functional subdomain from residues 301 to 333 assumes two distinctive structural elements with residues 301-322 adopting a well-packed hairpin structure followed by a flexible C-terminal tail. Furthermore, the backbone (15)N relaxation data demonstrate that the hairpin structure has significantly limited backbone motions, indicating a high conformational stability for the folded structure. Therefore, while the flexible C-terminal tail is suitable for binding to the PDZ domain, the folded hairpin may represent a latent structure requiring phosphorylation-induced conformational changes for high-affinity interactions with the SH2 domain.
Song
Jianxing
J
Biomolecular NMR Group and Mammalian Cells Genetics Group, Biotechnology Research Institute, National Research Council Canada, 6100 Royalmount Avenue, Montreal, Quebec, Canada H4P 2R2. Jianxing.Song@nrc.ca
Vranken
Wim
W
Xu
Ping
P
Gingras
Richard
R
Noyce
Ryan S
RS
Yu
Zhenbao
Z
Shen
Shi-Hsiang
SH
Ni
Feng
F
D000595:Amino Acid Sequence; D002462:Cell Membrane / Q000737:chemistry / Q000502:physiology; D003593:Cytoplasm / Q000737:chemistry* / Q000502:physiology; D036388:Ephrin-B2; D006801:Humans; D008024:Ligands; D008565:Membrane Proteins / Q000737:chemistry* / Q000502:physiology; D008969:Molecular Sequence Data; D009587:Nitrogen Isotopes; D019906:Nuclear Magnetic Resonance, Biomolecular / Q000379:methods; D010446:Peptide Fragments / Q000138:chemical synthesis / Q000737:chemistry / Q000502:physiology; D011487:Protein Conformation; D017434:Protein Structure, Tertiary / Q000502:physiology; D015398:Signal Transduction / Q000502:physiology; D012996:Solutions; D013816:Thermodynamics
D036388:Ephrin-B2; D008024:Ligands; D008565:Membrane Proteins; D009587:Nitrogen Isotopes; D010446:Peptide Fragments; D012996:Solutions