Structural and functional relationships between h- and l-caldesmons.
Two different Mr forms of caldesmon as judged by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (Mr values in the range of 120,000-150,000, h-caldesmon and 70,000-80,000, l-caldesmon) have been already identified. h-Caldesmon is predominantly expressed in smooth muscle cells, whereas l-caldesmon widely distributes in non-muscle cells. Most recently, the molecular cloning of h-caldesmon has been reported (Hayashi, K., Kanda, K., Kimizuka, F., Kato, I., and Sobue, K. (1989) Biochem. Biophys. Res. Commun. 164, 503-511; Bryan, J., Imai, M., Lee, R., Moore, P., Cook, R. G., and Lin, W-G. (1989) J. Biol. Chem. 264, 13873-13879). The calculated Mr of this protein from its primary structure is 88,743. Here, the nucleotide and deduced amino acid sequences of l-caldesmon have been determined by cloning and sequencing the cDNA from chick brain and compared with those of h-caldesmon. The l-caldesmon cDNA encodes a sequence of 517 amino acids with the calculated Mr of 58,844. Two isoforms of caldesmon conserve the completely identical sequences in the NH2- and COOH-terminal domains except for the insertion of Ala-508 in l-caldesmon. Interestingly, the central repeating sequence of h-caldesmon (residues 201-447) is deleted in the l-caldesmon molecule. The short NH2-terminals of two caldesmons individually show the unique sequences. The results of Northern and Southern blot analyses suggest that two mRNAs (4.8 and 4.1 kilo-bases) coding for caldesmon isoforms may be generated from a single gene by alternative splicing. Using a series of truncated caldesmons expressed in Escherichia coli, the common calmodulin-, tropomyosin-, and actin-binding sites and the minimum regulatory domains, which are involved in the Ca2(+)-dependent regulation of actin-myosin interaction, have been identified within the limited consensus sequences (residues 381-433 for l-caldesmon and residues 636-688 for h-caldesmon).
Hayashi
K
K
Department of Neurochemistry and Neuropharmacology, Osaka University Medical School, Japan.
Fujio
Y
Y
Kato
I
I
Sobue
K
K
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001921:Brain / Q000378:metabolism; D002147:Calmodulin / Q000494:pharmacology; D002148:Calmodulin-Binding Proteins / Q000235:genetics* / Q000302:isolation & purification / Q000494:pharmacology; D002645:Chickens; D003001:Cloning, Molecular; D004247:DNA / Q000235:genetics / Q000302:isolation & purification; D004926:Escherichia coli / Q000235:genetics; D007700:Kinetics; D008969:Molecular Sequence Data; D009218:Myosins / Q000378:metabolism; D015345:Oligonucleotide Probes; D010957:Plasmids; D011994:Recombinant Proteins / Q000302:isolation & purification / Q000494:pharmacology; D015183:Restriction Mapping; D013728:Terminator Regions, Genetic
D002147:Calmodulin; D002148:Calmodulin-Binding Proteins; D015345:Oligonucleotide Probes; D011994:Recombinant Proteins; D004247:DNA; D009218:Myosins