Expression and purification of a convenient Ca2+-calmodulin-dependent protein kinase II GST-fusion substrate

Abundant and convenient protein substrates are extremely useful tools for studying protein kinases. However, few such substrates exist for alpha-Ca(2+)-calmodulin-dependent protein kinase II (CaMKII) and those that are available are generally small and expensive peptides that are cumbersome to use....

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Bibliographic Details
Published in:Protein expression and purification 2002-12, Vol.26 (3), p.343-348
Main Authors: Miroy, Greta, Monteiro, Mervyn J
Format: Article
Language:English
Subjects:
Amino Acid Sequence
Calcium-Calmodulin-Dependent Protein Kinase Type 2
Calcium-Calmodulin-Dependent Protein Kinases - metabolism
Chromatography, Affinity
Cloning, Molecular
Glutathione Transferase - genetics
Glutathione Transferase - metabolism
Glycogen Synthase - chemistry
Glycogen Synthase - genetics
Glycogen Synthase - metabolism
Kinetics
Molecular Sequence Data
Recombinant Fusion Proteins - biosynthesis
Recombinant Fusion Proteins - genetics
Recombinant Fusion Proteins - isolation & purification
Recombinant Fusion Proteins - metabolism
Substrate Specificity
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Summary:Abundant and convenient protein substrates are extremely useful tools for studying protein kinases. However, few such substrates exist for alpha-Ca(2+)-calmodulin-dependent protein kinase II (CaMKII) and those that are available are generally small and expensive peptides that are cumbersome to use. The GST-fusion expression system was used to express a 10 amino acid substrate of CaMKII PLRRTLSVAA in bacteria. Using glutathione-agarose affinity chromatography, we obtained milligram quantities of the highly purified recombinant GST-fusion protein. The GST-fusion protein was tested for its efficacy and specificity as a substrate for CaMKII in phosphorylation assays using recombinant enzyme and radiolabeled [gamma-32P]ATP. The reaction products of these phosphorylation assays were resolved by electrophoresis in SDS-polyacrylamide gels and quantified by phosphoimage analysis. It was found that compared to a phosphorylation-null substrate, GST-PLRRTLAVAA, in which the phosphorylated target serine residue was mutated to an alanine, the GST-PLRRTLSVAA substrate was phosphorylated by CaMKII with an apparent K(m) of 18 microM, indicating that the latter is a highly effective substrate for this enzyme.
ISSN:1046-5928
DOI:10.1016/S1046-5928(02)00557-0