Twenty-eight-kilodalton phosphorylatable calcium- and lipid-binding proteins purified from Physarum plasmodium.
Two 28-kDa calcium- and lipid-binding proteins were isolated from a detergent-insoluble fraction of the Physarum plasmodium. Both proteins have molecular masses of approximately 28 kDa by SDS-PAGE. The protein designated 28K-I has a slightly lower mobility than that designated 28K-II. The purified 28K-I has a dissociation constant of 1.0 microM for Ca2+ ions, while the 28K-II has two different dissociation constants: one of 0.32 microM and the other of 3.2 mM. The 28K-I binds to liposomes at Ca2+ concentrations higher than 1.0 microM and has a dissociation constant for lipid of 34 micrograms/ml at 10 microM Ca2+. The 28K-II binds to liposomes at concentrations of Ca2+ above the mM range and has a dissociation constant of 36 micrograms/ml for lipid at 2 mM Ca2+. There is no evidence of actin-binding activity by either of the 28-kDa (28K) proteins. The 28K proteins crossreacted with an antiserum against chicken brush border calpactin I. The two proteins have quite different phosphorylation levels between a fraction prepared from the cytosolic endoplasm and a fraction prepared from the whole cell. The 28K proteins may play some role in the membrane structure dynamics of the cortical gel layer.
Ogihara
S
S
Department of Biology, College of General Education, Osaka University.
Sesaki
H
H
D000199:Actins / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002135:Calcium-Binding Proteins / Q000737:chemistry / Q000302:isolation & purification* / Q000378:metabolism; D002352:Carrier Proteins / Q000737:chemistry / Q000302:isolation & purification* / Q000378:metabolism; D002846:Chromatography, Affinity; D003600:Cytosol / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D005656:Fungal Proteins / Q000737:chemistry / Q000302:isolation & purification* / Q000378:metabolism; D050356:Lipid Metabolism; D008081:Liposomes / Q000378:metabolism; D008970:Molecular Weight; D010766:Phosphorylation; D010804:Physarum / Q000378:metabolism*
D000199:Actins; D002135:Calcium-Binding Proteins; D002352:Carrier Proteins; D005656:Fungal Proteins; D008081:Liposomes; D002118:Calcium