CLONING AND CHARACTERIZATION OF ALPHA(PS1), A NOVEL DROSOPHILA-MELANOGASTER INTEGRIN

The Drosophila position-specific integrins (PS integrins or PS antigen s) comprise two heterodimeric complexes, alpha(PS1)beta(PS) and alpha( PS2)beta(PS). With the cloning of alpha(PS1), described here, we compl ete the characterization of the primary structure of the three PS inte grin subunits. We have purified the alpha(PS1) subunit, obtained pepti de sequence and isolated genomic and cDNA clones. The encoded alpha(PS 1) protein contains the cysteine pattern of the cleaved alpha integrin s, three putative metal binding domains and shows the other characteri stic features of alpha integrins. Regions of sequence variation indica te that alpha(PS1) is distinct from all other alpha chains. The transc ript analysis shows that the patterns of both alpha(PS1) mRNA and prot ein expression are the same, suggesting that the gene is controlled tr anscriptionally. We compare the gene structures of the Drosophila alph a(PS1), alpha(PS2), the human alpha(IIb) and alpha(X) (p150,95) and th e C elegans F54G8.3 integrins. We find several positions and phases of introns conserved which, supported by conservation also in the amino acid sequence, indicates that they all derive from a common ancestral gene.