| Abstract: | Ligatin is a filamentous plasma membrane protein that serves as a baseplate for the attachment of peripheral glycoproteins to the external cell surface. Ligatin can be released from intact, embryonic chick neural retinal cells by treatment with 20 mM Ca++ without adversely affecting their viability. α-Glucose-1-phos phate is also effective in removing ligatin-associated glycoproteins from intact cells. After either of these treatments, the retinal cells seem not to exhibit Ca++ -dependent adhesion for one another. It is thus suggested that ligatin in neural retina may serve as a baseplate for the attachment to the cell surface of glycoproteins active in Ca++-dependent adhesion. The finding that Ca++ serves to protect Ca++-dependent adhesion molecules from digestion by trypsin is discussed in relation to steric constraints on trypsin's accessibility to these adhesion molecules because of their possible binding to arrayed ligatin filaments. |
