The accessibility of certain proteins on embryonic chick neural retina cells to iodination and tryptic removal is altered by calcium.
We have used cell-surface-specific labelling techniques and two-dimensional gel electrophoresis to identify proteins on embryonic chick neural retina cells and to determine the effects of Ca2+ on their accessibility to labelling and tryptic removal. A number of proteins on these cells are, in the presence of Ca2+, relatively inaccessible to iodination and/or tryptic removal. Of these, a glycoprotein of Mr approx. 130 x 10(3), with a pI of approx. 4.8, is the major cell-surface-iodinatable species that is retained during trypsinization in the presence of Ca2+. The removal of Ca2+ renders this glycoprotein much more accessible to both procedures. Its accessibility to these probes decreases on re-addition of Ca2+. The accessibility of its oligosaccharide moiety to galactose oxidase is, however, unaltered by the removal of Ca2+. These characteristics, together with immunological data presented elsewhere suggest that this glycoprotein may be a component of the Ca2+-dependent adhesive system that can be demonstrated on these cells.
D000818:Animals; D001345:Autoradiography; D002118:Calcium / Q000494:pharmacology*; D002448:Cell Adhesion; D002642:Chick Embryo; D004586:Electrophoresis; D005136:Eye Proteins / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D008565:Membrane Proteins / Q000378:metabolism; D008970:Molecular Weight; D011193:Potassium Iodide / Q000494:pharmacology; D012160:Retina / Q000166:cytology / Q000196:embryology / Q000378:metabolism*; D014357:Trypsin
D005136:Eye Proteins; D008565:Membrane Proteins; D011193:Potassium Iodide; D014357:Trypsin; D002118:Calcium