Crystal structure of the C-terminal tetrad repeat from synexin (annexin VII) of Dictyostelium discoideum.
Synexin (annexin VII) is a cytosolic Ca(2+)-binding protein that promotes membrane fusion and forms voltage-regulated ion channels in artificial and natural membranes. The crystal structure of the C-terminal tetrad repeat from recombinant synexin (annexin VII) of Dictyostelium discoideum was solved to 2.45 A resolution. The protein crystallized in a dimeric form with two molecules joined face-to-face by their convex sides. Mainly hydrogen bonds and van der Waals contacts are involved in dimer formation, while not Ca2+ is bound to the conserved Ca(2+)-binding sites. The truncated N terminus is folded into a short antiparallel beta-sheet, from which the side-chain of Tyr111 penetrates sideways into the central, hydrophilic pore and may directly affect the ion channel activity. In order to investigate the structure of the missing N-terminal domain, we synthesized a 37-membered peptide of the N-terminal tail, (GYPPQQ)6G. CD and NMR studies showed a random coil conformation of the peptide in solution, suggesting for the synexin N terminus the lack of a well-ordered, three-dimensional fold.
Liemann
S
S
Abteilungen für Strukturforschung, Max-Planck-Institut für Biochemie, Martinsried, Germany.
Bringemeier
I
I
Benz
J
J
Göttig
P
P
Hofmann
A
A
Huber
R
R
Noegel
A A
AA
Jacob
U
U
D000595:Amino Acid Sequence; D000818:Animals; D017310:Annexin A7 / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D001665:Binding Sites; D002942:Circular Dichroism; D018360:Crystallography, X-Ray; D004023:Dictyostelium / Q000737:chemistry*; D019281:Dimerization; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000138:chemical synthesis / Q000737:chemistry; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D012091:Repetitive Sequences, Nucleic Acid; D017386:Sequence Homology, Amino Acid
D017310:Annexin A7; D010446:Peptide Fragments