The top loops of the C(2) domains from synaptotagmin and phospholipase A(2) control functional specificity.
The phospholipid-binding specificities of C(2) domains, widely distributed Ca(2+)-binding modules, differ greatly despite similar three-dimensional structures. To understand the molecular basis for this specificity, we have examined the synaptotagmin 1 C(2)A domain, which interacts in a primarily electrostatic, Ca(2+)-dependent reaction with negatively charged phospholipids, and the cytosolic phospholipase A(2) (cPLA(2)) C(2) domain, which interacts by a primarily hydrophobic Ca(2+)-dependent mechanism with neutral phospholipids. We show that grafting the short Ca(2+)-binding loops from the tip of the cPLA(2) C(2) domain onto the top of the synaptotagmin 1 C(2)A domain confers onto the synaptotagmin 1 C(2)A domain the phospholipid binding specificity of the cPLA(2) C(2) domain, indicating that the functional specificity of C(2) domains is determined by their short top loops.
Gerber
S H
SH
Center for Basic Neuroscience, Department of Molecular Genetics, and Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA.
Rizo
J
J
Südhof
T C
TC
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002135:Calcium-Binding Proteins; D017931:DNA Primers; D005982:Glutathione Transferase / Q000378:metabolism; D006801:Humans; D008562:Membrane Glycoproteins / Q000737:chemistry / Q000378:metabolism*; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000737:chemistry / Q000378:metabolism*; D010741:Phospholipases A / Q000737:chemistry / Q000378:metabolism*; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D050863:Synaptotagmin I; D050857:Synaptotagmins
D002135:Calcium-Binding Proteins; D017931:DNA Primers; D008562:Membrane Glycoproteins; D009419:Nerve Tissue Proteins; D011993:Recombinant Fusion Proteins; C494310:SYT1 protein, human; D050863:Synaptotagmin I; C494312:Syt1 protein, rat; D050857:Synaptotagmins; D005982:Glutathione Transferase; D010741:Phospholipases A