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cDNAs Encoding the β Subunit of Cap Z, the Actin-capping Protein of the Z Line of Muscle

1989; Elsevier BV; Volume: 264; Issue: 21 Linguagem: Inglês

10.1016/s0021-9258(18)63905-5

1083-351X

Jane E. Caldwell, James A. Waddle, John A. Cooper, J A Hollands, Samuel J. Casella, James F. Casella,

Biotin and Related Studies

Three cDNAs encoding the B chain of Cap Z have been isolated from X g t l l 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 , = 31,352.The predicted protein sequence contains eight regions that match perfectly the NHz-terminal sequence of eight peptides isolated from muscle Cap Z B. The amino acid compositions of the protein predicted from the cDNA sequence and Cap Z j3 are similar.Comparison of the cDNA sequence and the predicted protein se- quence 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.Cap Z is a heterodimeric protein with subunits of M, = 36,000 ( a subunit) and 32,000 ( p subunit).Cap Z binds to the barbed ends of actin filaments in uitro and is located at the Z line in skeletal muscle (Casella et al., 1986;Casella et al., 1987).Since the barbed ends of actin filaments are also located at the Z line, Cap Z may attach actin filaments to the Z line.Cap Z is a member of a family of actin-binding proteins, called "capping proteins," (reviewed in Pollard and Cooper, 1986) that are heterodimers, bind the barbed ends of actin filaments,