The amino acid sequences of chick and slime mould alpha-actinin each contain four repeats of approximately 122 residues. These repeats are homologous to the 18-22 repeats, each of approximately 106 residues, found in the alpha and beta subunits of spectrin and fodrin, and to the multiple repeats of approximately 110 residues found in the Duchenne muscular dystrophy protein (dystrophin). The repeats correspond to the elongated rod-like portion of these molecules. We present a multiple sequence alignment of 21 repeats from this superfamily (8 alpha-actinin and 13 spectrin/fodrin), based on optimal pairwise alignments, from which a characteristic consensus pattern of amino acid types is deduced. Trp 46 is invariant in all but one repeat, and physicochemical classes of amino acids are conserved at 25 other positions. Secondary structure prediction on both the alpha-actinin and spectrin repeats taken together with the distribution of proline residues in the sequences, strongly suggest that each repeated domain consists of a four-helix structure. Our predictions differ significantly from previous three-helix models based on analyses of fewer sequences. To determine possible interdomain regions, sites of limited proteolysis of the native chick alpha-actinin dimer were determined and located in the amino acid sequence. The majority of these sites were in corresponding positions in different repeats within a segment predicted as a long helix. We propose a model, consistent with the overall dimensions of the rod-like portions of the molecules, in which these long, probably interrupted helices, link adjacent domains.

We have isolated and sequenced a 2.1-kilobase cDNA encoding 86% of the sequence of alpha-actinin. The cDNA clone was isolated from a chick embryo fibroblast cDNA library constructed in the expression vector lambda gt11. Identification of this sequence as alpha-actinin was confirmed by immunological methods and by comparing the deduced protein sequence with the sequence of several CNBr fragments obtained from adult chicken smooth muscle (gizzard) alpha-actinin. The deduced protein sequence shows two distinct domains, one of which consists of four repeats of approximately 120 amino acids. This region corresponds to a previously identified 50-kDa tryptic peptide involved in formation of the alpha-actinin dimer. The last 19 residues of C-terminal sequence display an homology with the so-called E-F hand of Ca2+-binding proteins. Hybridization analysis reveals only one size of mRNA (approximately 3.5 kilobases) in fibroblasts, but multiple bands in genomic cDNA.

We have sequenced a cDNA, isolated from a chick embryo fibroblast lambda gt11 library, that encodes all 887 amino acids of alpha-actinin. Sequence from 10 different peptides from chick smooth muscle alpha-actinin was found to match that derived from the cDNA. The deduced protein sequence can be divided into three distinct domains: (a) the N-terminal 240 amino acid contains a highly conserved region (compared with Dictyostelium alpha-actinin) which probably represents the actin-binding domain, (b) amino acids 270-740 contain four repeats of a spectrin-like sequence, and (c) the C-terminal sequence contains two EF-hand Ca2+-binding sites. Each of these sites is defective in at least one oxygen-containing Ca2+-chelating amino acid side chain, suggesting that they are nonfunctional. Southern blots suggest that the alpha-actinin cDNA described here hybridizes to only one gene in chicken. Northern blots reveal only one size class of mRNA in fibroblasts and smooth muscle, but no hybridizing species could be detected in skeletal muscle poly(A+) RNA. The results are consistent with the view that smooth and skeletal muscle alpha-actinins are encoded by separate genes, which are considerably divergent.

Conference Article| October 01 1987 The structure and function of α-actinin MICHAEL D. BARON; MICHAEL D. BARON 1Department of Biochemistry, University of Leicester, University Road, Leicester LE1 7RH, U.K. Search for other works by this author on: This Site PubMed Google Scholar MATTHEW D. DAVISON; MATTHEW D. DAVISON 1Department of Biochemistry, University of Leicester, University Road, Leicester LE1 7RH, U.K. Search for other works by this author on: This Site PubMed Google Scholar PETER JONES; PETER JONES 1Department of Biochemistry, University of Leicester, University Road, Leicester LE1 7RH, U.K. Search for other works by this author on: This Site PubMed Google Scholar DAVID R. CRITCHLEY DAVID R. CRITCHLEY 1Department of Biochemistry, University of Leicester, University Road, Leicester LE1 7RH, U.K. Search for other works by this author on: This Site PubMed Google Scholar Author and article information Publisher: Portland Press Ltd Received: May 11 1987 Online ISSN: 1470-8752 Print ISSN: 0300-5127 © 1987 Biochemical Society1987 Biochem Soc Trans (1987) 15 (5): 796–798. https://doi.org/10.1042/bst0150796 Article history Received: May 11 1987 Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Icon Share Facebook Twitter LinkedIn Email Cite Icon Cite Get Permissions Citation MICHAEL D. BARON, MATTHEW D. DAVISON, PETER JONES, DAVID R. CRITCHLEY; The structure and function of α-actinin. Biochem Soc Trans 1 October 1987; 15 (5): 796–798. doi: https://doi.org/10.1042/bst0150796 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentAll JournalsBiochemical Society Transactions Search Advanced Search Keywords: CNBr, cyanogen bromide This content is only available as a PDF. © 1987 Biochemical Society1987 Article PDF first page preview Close Modal You do not currently have access to this content.