Structure of human placental microvilli.
Cytoskeletons have been prepared from microvilli isolated from the human placental syncytiotrophoblast. They contain actin and a protein similar to fimbrin. In addition, they contain calmodulin and a protein of relative molecular mass (Mr) 105 000, both of which can be released from the cytoskeletons by treatment with Ca2+. In this respect the 105 000 Mr protein is more similar to non-muscle alpha-actinin than to the intestinal microvillar protein with an Mr of 110 000. Human placental actin displays the anomalous properties of binding to phenyl-Sepharose and wheatgerm agglutinin-Sepharose, suggesting that one or more membrane glycoproteins is associated with the actin. Transferrin, presumably receptor-bound, has been identified in preparations of extensively washed placental microvillar cytoskeletons. These findings are discussed in terms of the earliest events in endocytosis and materno-fetal transfer.
D000199:Actins / Q000502:physiology; D002147:Calmodulin; D002462:Cell Membrane / Q000648:ultrastructure*; D003599:Cytoskeleton / Q000032:analysis / Q000648:ultrastructure; D004591:Electrophoresis, Polyacrylamide Gel; D005260:Female; D006801:Humans; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; D008840:Microfilament Proteins; D008871:Microvilli / Q000648:ultrastructure*; D008970:Molecular Weight; D010920:Placenta / Q000648:ultrastructure*; D011247:Pregnancy; D014168:Transferrin / Q000032:analysis
D000199:Actins; D002147:Calmodulin; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; D008840:Microfilament Proteins; D014168:Transferrin; C026742:plastin