The ligand-binding face of the semaphorins revealed by the high-resolution crystal structure of SEMA4D.

Journal article

Semaphorins, proteins characterized by an extracellular sema domain, regulate axon guidance, immune function and angiogenesis. The crystal structure of SEMA4D (residues 1-657) shows the sema topology to be a seven-bladed beta-propeller, revealing an unexpected homology with integrins. The sema beta-propeller contains a distinctive 77-residue insertion between beta-strands C and D of blade 5. Blade 7 is followed by a domain common to plexins, semaphorins and integrins (PSI domain), which forms a compact cysteine knot abutting the side of the propeller, and an Ig-like domain. The top face of the beta-propeller presents prominent loops characteristic of semaphorins. In addition to limited contact between the Ig-like domains, the homodimer is stabilized through extensive interactions between the top faces in a sector of the beta-propeller used for heterodimerization in integrins. This face of the propeller also mediates ligand binding in integrins, and functional data for semaphorin-receptor interactions map to the equivalent surface.

Authors: Love, C; Harlos, K; Mavaddat, N; Davis, S; Stuart, D

• Publication status: Published
• Journal: Nature structural biology
• Volume: 10
• Issue: 10
• Pages: 843-848
• Publication date: 2003-10-01
• DOI: 10.1038/nsb977
• ISSN: 1072-8368
• Language: English
• Keywords: Amino Acid Sequence; Protein Binding; Ligands; Protein Structure, Tertiary; Crystallography, X-Ray; Dimerization; Membrane Glycoproteins; Humans; Semaphorins; Molecular Sequence Data; Antigens, CD