Isolation and characterization of three forms of 36-kDa Ca2+-dependent actin- and phospholipid-binding proteins from human placenta membrane.
We purified three forms of 36-kDa proteins, two monomeric 36-kDa proteins, which had pIs of 7.5 (36K-I) and 6.4 (36K-II), and one 36-kDa complex (36K-C) consisting of two subunits, 36-kDa (pI 7.5) and 12-kDa (pI 5.8), from human placenta membrane. The 36-kDa subunit of 36K-C was identical to 36K-I as judged by pI, cyanogen bromide peptide mapping and immunological cross-reactivity. The three proteins showed F-actin- and phosphatidylserine-binding abilities dependent on Ca2+ concentrations at millimolar and micromolar levels, respectively. They all had phospholipase A2 inhibitory activity. Only 36K-II was phosphorylated extensively at tyrosine residue in Ca2+- and EGF- dependent manners in the membrane fraction of A431 cells. 36K-I was the best substrate for src kinase, whereas 36K-II was the best for fps kinase. However, 36K-C was not phosphorylated by any kinases used here.
D002118:Calcium / Q000378:metabolism*; D002352:Carrier Proteins / Q000302:isolation & purification*; D006801:Humans; D007526:Isoelectric Point; D008565:Membrane Proteins; D008566:Membranes / Q000032:analysis; D008840:Microfilament Proteins / Q000302:isolation & purification*; D008970:Molecular Weight; D010449:Peptide Mapping; D010718:Phosphatidylserines / Q000378:metabolism; D010741:Phospholipases A / Q000037:antagonists & inhibitors; D054467:Phospholipases A2; D049294:Phospholipid Transfer Proteins; D010766:Phosphorylation; D010920:Placenta / Q000032:analysis*
D002352:Carrier Proteins; D008565:Membrane Proteins; D008840:Microfilament Proteins; D010718:Phosphatidylserines; D049294:Phospholipid Transfer Proteins; D010741:Phospholipases A; D054467:Phospholipases A2; D002118:Calcium