Figure 1.

Summary of the chick β1 subunits tested and the results obtained. The sequences of the wild-type (WT) cytoplasmic domain and the point and deletion mutations within it are shown. The D154A mutation in the extracellular domain is shown in a schematic representation of the entire β1 integrin subunit, with the transmembrane domain indicated in black. Those chick β1 subunits that had activity in the keratinocyte differentiation assay were all equally effective, and the results are therefore summarized as “++” (see Figure 6). The subunits differed in activity in the SCC4 assay (see Figure 7), and a positive effect is therefore summarized as “++” or “+.”