cDNAs encoding the β subunit of Cap Z, the actin-capping protein of the Z line of muscle

Three cDNAs encoding the β chain of Cap Z have been isolated from λgt11 chicken libraries screened with antibodies. The coding region, which is identical among the cDNAs, contains 831 basepairs encoding a protein with 277 amino acid residues and M(r) = 31,352. The predicted protein sequence contains eight regions that match perfectly the NH₂-terminal sequence of eight peptides isolated from muscle Cap Z β. The amino acid compositions of the protein predicted from the cDNA sequence and Cap Z β are similar. Comparison of the cDNA sequence and the predicted protein sequence with those of other actin-binding proteins and all sequences in the GenBank and NBRF Protein databases shows no remarkable similarities. Two of the three cDNAs contain the complete coding region. Both coding regions begin with a consensus translation start site; however, their 5'-untranslated regions are different. Northern analysis of whole chicken embryos and adult chicken tissues shows two mRNA species. The embryo and non-muscle tissues have transcripts of 1.35 and 2.00 kilobases, and the muscle tissues have transcripts of 2.15 and 1.45 kilobases. Southern analysis of chicken genomic DNA shows that there are probably two related genes, one more similar to the cDNA than the other.