Structure-function relationships in sorcin, a member of the penta EF-hand family. Interaction of sorcin fragments with the ryanodine receptor and an Escherichia coli model system.
Sorcin, a 21.6 kDa cytosolic EF-hand protein which undergoes a Ca(2+)-induced translocation from cytoplasm to membranes, has been assigned to the newly defined penta EF-hand family. A molecular model of the C-terminal Ca(2+)-binding domain has been generated using as a template the X-ray coordinates of the corresponding domain in the calpain light subunit, the family prototype [Lin, G., et al. (1997) Nat. Struct. Biol. 4, 539-546]. The model indicates that in sorcin the three-dimensional structure is conserved and in particular that of EF1, the novel EF-hand motif characteristic of the family. On this basis, two stable fragments have been obtained and characterized. Just like the native protein, the sorcin Ca(2+)-binding domain (residues 33-198) is largely dimeric, interacts with the ryanodine receptor at physiological calcium concentrations, and undergoes a reversible, Ca(2+)-dependent translocation from cytosol to target proteins on Escherichia coli membranes. In contrast, the 90-198 fragment (residues 90-198), which lacks EF1 and EF2, does not bind Ca(2+) with high affinity and is unable to translocate. Binding of calcium to the EF1-EF2 pair is therefore required for the activation of sorcin which uses the C-terminal calcium-binding domain for interaction with the ryanodine receptor, a physiological target in muscle cells.
Zamparelli
C
C
CNR Center of Molecular Biology, Department of Biochemical Sciences "A. Rossi Fanelli", University of Rome "La Sapienza", 00185 Rome, Italy.
Ilari
A
A
Verzili
D
D
Giangiacomo
L
L
Colotti
G
G
Pascarella
S
S
Chiancone
E
E
D000595:Amino Acid Sequence; D001665:Binding Sites; D002118:Calcium / Q000737:chemistry / Q000378:metabolism; D002135:Calcium-Binding Proteins / Q000737:chemistry* / Q000378:metabolism / Q000502:physiology*; D020832:EF Hand Motifs; D004926:Escherichia coli / Q000737:chemistry*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry* / Q000378:metabolism; D017434:Protein Structure, Tertiary; D019837:Ryanodine Receptor Calcium Release Channel / Q000737:chemistry* / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013329:Structure-Activity Relationship
D002135:Calcium-Binding Proteins; D010446:Peptide Fragments; D019837:Ryanodine Receptor Calcium Release Channel; D002118:Calcium