Identification of functioning regulatory sites and a new myosin binding site in the C-terminal 288 amino acids of caldesmon expressed from a human clone.
A partial clone of caldesmon, coding for the C-terminal 288 amino acids, was isolated from a human fetal liver cDNA library and sequenced. Expression of the clone in Escherichia coli produced a peptide called H1 (M(r) 32,549), which inhibited tropomyosin-enhanced actomyosin Mg(2+)-ATPase activity by 90% with half maximal inhibition at 0.03-0.04 mol H1 per mol actin. The inhibition could be reversed by Ca(2+)-calmodulin. H1 bound actin, Ca(2+)-calmodulin and tropomyosin and smooth muscle myosin with high affinities. This latter finding shows the presence of a second myosin-binding site in caldesmon. This was confirmed in thrombic digests of native sheep aorta and chicken gizzard caldesmon.
Huber
P A
PA
National Heart and Lung Institute, London, UK.
Redwood
C S
CS
Avent
N D
ND
Tanner
M J
MJ
Marston
S B
SB
D000199:Actins / Q000494:pharmacology; D000205:Actomyosin / Q000037:antagonists & inhibitors; D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D017301:Ca(2+) Mg(2+)-ATPase / Q000037:antagonists & inhibitors; D002118:Calcium / Q000378:metabolism; D002147:Calmodulin / Q000378:metabolism; D002148:Calmodulin-Binding Proteins / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology; D002645:Chickens / Q000235:genetics; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000235:genetics; D006801:Humans; D008099:Liver / Q000737:chemistry; D008969:Molecular Sequence Data; D009130:Muscle, Smooth / Q000737:chemistry; D009218:Myosins / Q000378:metabolism* / Q000494:pharmacology; D009928:Organ Specificity; D010446:Peptide Fragments / Q000378:metabolism / Q000494:pharmacology; D011993:Recombinant Fusion Proteins / Q000378:metabolism / Q000494:pharmacology; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D012756:Sheep; D013045:Species Specificity; D014335:Tropomyosin / Q000037:antagonists & inhibitors
D000199:Actins; D002147:Calmodulin; D002148:Calmodulin-Binding Proteins; D018076:DNA, Complementary; D010446:Peptide Fragments; D011993:Recombinant Fusion Proteins; D014335:Tropomyosin; D000205:Actomyosin; D017301:Ca(2+) Mg(2+)-ATPase; D009218:Myosins; D002118:Calcium