Immunochemical evidence for the binding of caldesmon to the NH2-terminal segment of actin.
The binding of caldesmon and its actin-binding fragments to actin was studied by using peptide antibodies directed against two actin sites implicated in actomyosin interactions. Antibodies against residues 1-7 on skeletal alpha-actin strongly inhibited the binding of caldesmon to actin and perturbed to a smaller extent the interaction between actin and the actin binding fragments. Carbodiimide coupling of ethylenediamine to the NH2-terminal acidic residues on actin inhibited the binding of caldesmon and its fragments to actin to a similar extent as the (residues 1-7) antibodies. Antibodies against residues 18-28 showed only limited competition with caldesmon for the binding to actin. These results lead to the following conclusions. (i) The NH2-terminal residues on actin play an important role in the binding of caldesmon to actin, (ii) residues 18-28 on actin do not form a major caldesmon interaction site, and (iii) the actin-binding fragments do not contain the full actin-binding interface. These conclusions and other literature data suggest that caldesmon regulates the actomyosin ATPase by competing with myosin.ATP for the NH2-terminal segment on actin.
Adams
S
S
Department of Chemistry and Biochemistry, University of California, Los Angeles 90024.
DasGupta
G
G
Chalovich
J M
JM
Reisler
E
E
D000199:Actins / Q000276:immunology / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D000906:Antibodies / Q000378:metabolism; D001665:Binding Sites; D001667:Binding, Competitive; D002148:Calmodulin-Binding Proteins / Q000378:metabolism*; D004797:Enzyme-Linked Immunosorbent Assay; D007140:Immunoglobulin Fab Fragments / Q000378:metabolism; D007074:Immunoglobulin G / Q000378:metabolism; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000276:immunology / Q000378:metabolism; D011817:Rabbits
D000199:Actins; D000906:Antibodies; D002148:Calmodulin-Binding Proteins; D007140:Immunoglobulin Fab Fragments; D007074:Immunoglobulin G; D010446:Peptide Fragments