AbstractThe basement membrane protein laminin‐5 promotes cell adhesion and migration. The carboxyl‐terminal G3 domain in the α3 chain is essential for the unique activity of laminin‐5. To investigate the function of the G3 domain, we prepared various recombinant laminin‐5 forms with a partially deleted or mutated G3 domain. The deletion of the carboxyl‐terminal 28 amino acids (region III) markedly decreased the cell adhesion activity with a slight loss of the cell motility activity toward BRL and EJ‐1 cells. This change was attributed to the loss of Lys‐Arg‐Asp sequence. Further deletion of 83 amino acids (region II) led to almost complete loss of the cell motility activity. All charged amino acid residues tested in this region were not responsible for the activity loss. These results suggest that the G3 domain contains two distinct regions that differently regulate cell adhesion and migration. Analysis of laminin‐5 receptors showed that integrins α3β1, α6β1, and α6β4 had different but synergistic effects on cell adhesion and migration on laminin‐5. However, the structural change of the G3 domain appeared not to change integrin specificity. The present study demonstrates that the G3 domain in laminin‐5 plays a central role to produce different biological effects on cells. © 2002 Wiley‐Liss, Inc.