Sequence of an unusually large protein implicated in regulation of myosin activity in C. elegans

Abstract

The Caenorhabditis elegans gene unc-22 encodes a very large muscle protein, called twitchin, which consists of a protein kinase domain and several copies of two short motifs. The sequence of twitchin has unexpected similarities to the sequences of proteins of the immunoglobulin superfamily, cell adhesion molecules and vertebrate muscle proteins, including myosin light-chain kinase. These homologies, together with results from earlier genetic and molecular analyses, indicate that twitchin is involved in a novel mechanism of myosin regulation.

Members of the immunoglobulin superfamily in bacteria

“…Immunoglobulin superfamily domains are also found in intracellular proteins, such as in the giant muscle proteins twitchin and titin (Benian et al, 1989;Labeit & Kolmerer, 1995). Speculation as to when the immunoglobulin superfamily arose makes identification of prokaryotic examples interesting.…”

Isoform-specific Interaction of the Myosin-binding Proteins (MyBPs) with Skeletal and Cardiac Myosin Is a Property of the C-terminal Immunoglobulin Domain

“…Thus, MyBP-C and MyBP-H are members of the Ig superfamily (34,35). The IgC2 and Fn (III) repeats are conserved in human MyBP-C (36) and seem to be a common feature of other myosinassociated proteins (37)(38)(39)(40)(41)(42). The myosin binding domain of chicken MyBP-C has been mapped to a 14-kDa C-terminal, ␣-chymotryptic peptide, containing one IgC2 repeat (2).…”

Fibronectin type III‐like sequences and a new domain type in prokaryotic depolymerases with insoluble substrates

“…Amino acich in the individual sequences, which are identical to the consensus sequence, are also shown in bold. Partial comensus sequences of Fn3's in fibroneetin [26], titin [23], twitehin [24], eytotaetin [25], a protein-tyrosin© phosphata~¢ [27] and s~vcral cytokine receptors [281are shown below. A total con~nsus sequence (bottom) was constructed by showing residues conserved in at least 4 of the individual consensus sequences, with completely conserved re,~idugs in bold.…”

“…1). The latter and a proline are also conserved in FnYs of the eukaryotie proteins: titin [23], twitchin [24], cytotactin [25], fibron~tin [26], a protein-tyrosin¢ phosphatase [27] and several eytokiae receptors [28].…”