Identification and quantification of calcium-binding proteins in squid axoplasm

The identities and quantities of calcium-binding proteins were determined in axoplasm isolated from the squid giant axon. 45Ca-binding assays on nitrocellulose filters containing axoplasm proteins separated by SDS-polyacrylamide electrophoresis revealed 4 major calcium-binding bands. These included...

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Bibliographic Details
Published in:The Journal of neuroscience 1988-06, Vol.8 (6), p.2172-2182
Main Authors: Krinks, MH, Klee, CB, Pant, HC, Gainer, H
Format: Article
Language:English
Subjects:
Animals
Axons - ultrastructure
Biological and medical sciences
Calcineurin
Calcium Radioisotopes
Calcium-Binding Proteins - metabolism
Calmodulin - metabolism
Calmodulin-Binding Proteins - metabolism
Cytoplasm - metabolism
Decapodiformes - metabolism
Fundamental and applied biological sciences. Psychology
Invertebrates
Iodine Radioisotopes
Loligo
Molecular Weight
Mollusca
Phosphoprotein Phosphatases - metabolism
Physiology. Development
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Summary:The identities and quantities of calcium-binding proteins were determined in axoplasm isolated from the squid giant axon. 45Ca-binding assays on nitrocellulose filters containing axoplasm proteins separated by SDS-polyacrylamide electrophoresis revealed 4 major calcium-binding bands. These included the high-molecular-weight (Mr greater than 330 and 220 X 10(3] neurofilament proteins, an unidentified protein band that migrated around Mr 55,000, and a diverse group of proteins that migrated together around Mr 17,000. The low-molecular-weight (Mr 17,000) calcium-binding proteins could be resolved into calmodulin (ca. 120 mumol/kg axoplasm), 2 other Mr 17,000 calcium-binding proteins, and a small amount of calcineurin B. It is estimated that these calcium-binding proteins in squid axoplasm could theoretically bind about 1 mmol Ca2+/kg axoplasm. 125I-Calmodulin overlay and Western blot analyses disclosed a number of calmodulin-binding proteins in axoplasm. These included fodrin, calcineurin A, and Ca2+/CaM protein kinase II subunits.
ISSN:0270-6474
1529-2401
DOI:10.1523/jneurosci.08-06-02172.1988