VARIANT CDNAS ENCODING PROTEINS SIMILAR TO THE ALPHA-SUBUNIT OF CHICKEN CAPZ

Chicken adult muscle and liver cDNA libraries were screened with a cDNA, alpha-1, previously isolated from a chicken embryo library by screening with antibodies against the alpha subunit of chicken CapZ. cDNAs with a new coding region, called alpha-2, were found in addition to ones with the alpha-1 coding region. Alpha-2 predicts a protein sequence that matches exactly the N-terminal sequence of 5 peptides prepared from CapZ alpha purified from chicken muscle, while the protein sequence predicted by alpha-1 matches the peptides well, but not exactly. The predicted protein sequences of alpha-1 and alpha-2 are very similar to each other, and they are similar to those of the alpha subunit of capping protein from Dictyostelium [Hartmann et al., J. Biol. Chem. 163:5254-5254, 1989] and an actin-binding protein from Xenopus [Ankenbauer et al., Nature 342:822-824, 1989]. Other conserved features of the predicted primary and secondary structures are noted. Chicken alpha-1 and alpha-2 are transcribed in all of 7 adult chicken muscle and non-muscle tissues in comparable amounts by Northern analysis. Alpha-2 has four poly(A)+RNA transcripts, one of which is rare in liver. Alpha-1 has two transcripts. Alpha-1 and alpha-2 are encoded by different single-copy genes by Southern analysis of chicken genomic DNA.