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Updated: May 5, 2026

Assaying Protein Kinase Activity with Radiolabeled ATP
Published on: May 26, 2017
The IkappaB kinase complex (IKK) contains two kinase subunits, IKKalpha and IKKbeta, necessary for IkappaB
E Zandi1, D M Rothwarf, M Delhase
1Department of Pharmacology, University of California at San Diego, La Jolla 92093-0636, USA.
Abstract:
Recently we purified a 900 kDa cytokine-responsive IkappaB kinase complex (IKK) and molecularly cloned one of its subunits, IKKalpha, a serine kinase. We now describe the molecular cloning and characterization of IKKbeta, a second subunit of the IKK complex. IKKbeta is 50% identical to IKKalpha and like it contains a kinase domain, a leucine zipper, and a helix-loop-helix. Although IKKalpha and IKKbeta can undergo homotypic interaction, they also interact with each other and the functional IKK complex contains both subunits. The catalytic activities of both IKKalpha and IKKbeta make essential contributions to IkappaB phosphorylation and NF-kappaB activation. While the interactions between IKKalpha and IKKbeta may be mediated through their leucine zipper motifs, their helix-loop-helix motifs may be involved in interactions with essential regulatory subunits.
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