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 Vol. 8; no. 6; pp. 2172 - 2182
Main Authors:	Krinks, MH, Klee, CB, Pant, HC, Gainer, H
Format:	Journal Article
Language:	English
Published:	Washington, DC Soc Neuroscience 01-06-1988 Society for Neuroscience
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 Marine environment Proteins Cephalopoda Calcium Gel electrophoresis Giant neuron Axon Loligo pealei Invertebrata Mollusca Calmodulin
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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.
Bibliography:	ObjectType-Article-2 SourceType-Scholarly Journals-1 ObjectType-Feature-1 content type line 23 ObjectType-Article-1 ObjectType-Feature-2
ISSN:	0270-6474 1529-2401
DOI:	10.1523/jneurosci.08-06-02172.1988