title: Isolation and characterization of sea urchin egg spectrin: calcium modulation of the spectrin-actin interaction.
abstract: Sea urchin egg spectrin has been purified from a homogenate of unfertilized Strongylocentrotus purpuratus eggs using standard biochemical procedures. SDS-PAGE analysis of the molecule revealed a closely spaced, high molecular weight doublet at 237/234 kDa (present in an equimolar ratio). Rotary shadowed images of egg spectrin revealed a double-stranded, elongate, flexible rod-shaped contour, measuring 210 nm in length and approximately 4-8 nm in width. Additionally, this molecule is shown to be immunologically related to avian erythroid spectrin, since it crossreacts with antibodies prepared against the chicken erythrocyte alpha-spectrin/240 kDa subunit. The interaction of egg spectrin with actin was examined by sedimentation and falling-ball viscometry assays. The binding and cross linking properties of spectrin to actin demonstrate a unique Ca++-sensitive regulation at micromolar Ca++ concentrations. This observation provides new insight into the way Ca++ may regulate spectrin-actin interactions in vitro and further suggests possible structural and modulatory roles for egg spectrin in the developing sea urchin embryo.
mesh_terms: D000199:Actins / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D003599:Cytoskeleton / Q000378:metabolism; D005260:Female; D008970:Molecular Weight; D010063:Ovum / Q000378:metabolism*; D012617:Sea Urchins; D013049:Spectrin / Q000302:isolation & purification / Q000378:metabolism*; D014783:Viscosity
chemical_list: D000199:Actins; D013049:Spectrin; D002118:Calcium