SUMMARY

Immunological probes and cell-surface biochemical analysis are combined to identify a cell-surface glycoprotein, which appears to be involved in the formation of calcium-dependent adhesions among embryonic chick neural retina cells. Comparison of radioiodinated cells shows that adhesive-competent cells have at their surface two glycoproteins not present on non-adhesive cells. These two components (with Mr 130 x 10', pi 4-8 and M, 70 x io3, pi 4-8) are immunoprecipitable with adhesion-blocking antisera. A fraction derived from retina-conditioned medium, containing one major immunoprecipitable component, neutralizes the inhibitory activity of aggregation-inhibiting Fab ' fragments and competes in immunoprecipitation for the two glycoprotein components. The evidence suggests that one or both of these components is involved in the formation of calcium-dependent adhesions among embryonic chick neura