Calcium-sensitive, lipid-binding cytoskeletal proteins of the human placental microvillar region.
In this study we describe a group of Ca2+-sensitive proteins located in the microvillar region of the human placental syncytiotrophoblast. By following the distribution of proteins between the particulate and supernatant phases of detergent-solubilized microvilli in the presence of defined concentrations of free Ca2+, we demonstrate a class of proteins of subunit molecular weights 72,000, 69,000, 38,000, 36,000, and 32,000 that associate with both the cytoskeleton and lipid at high concentrations of free Ca2+. These proteins can be released from microvilli using EGTA-containing buffers. Although they do not bind to phenyl-Sepharose, they will bind to phospholipids immobilized on phenyl-Sepharose columns in a Ca2+-dependent manner and show a marked preference for phospholipids with negatively charged headgroups. The results provide evidence for a sequence of events which may occur within the microvillus as the localized concentration of intracellular free Ca2+ rises.
D002118:Calcium / Q000494:pharmacology*; D002824:Chorionic Villi / Q000378:metabolism* / Q000648:ultrastructure; D003598:Cytoskeletal Proteins / Q000302:isolation & purification / Q000378:metabolism*; D003599:Cytoskeleton / Q000032:analysis / Q000187:drug effects; D005260:Female; D006801:Humans; D008081:Liposomes / Q000378:metabolism; D008563:Membrane Lipids / Q000378:metabolism*; D008970:Molecular Weight; D010743:Phospholipids / Q000378:metabolism*; D011247:Pregnancy; D011257:Pregnancy Proteins / Q000302:isolation & purification / Q000378:metabolism*; D011485:Protein Binding
D003598:Cytoskeletal Proteins; D008081:Liposomes; D008563:Membrane Lipids; D010743:Phospholipids; D011257:Pregnancy Proteins; D002118:Calcium