1my5

From Proteopedia

Revision as of 10:49, 20 March 2008

NF-kappaB p65 subunit dimerization domain homodimer

Overview

IkappaBalpha inhibits transcription factor NF-kappaB activity by specific binding to NF-kappaB heterodimers composed of p65 and p50 subunits. It binds with slightly lower affinity to p65 homodimers and with significantly lower affinity to homodimers of p50. We have employed a structure-based mutagenesis approach coupled with protein-protein interaction assays to determine the source of this dimer selectivity exhibited by IkappaBalpha. Mutation of amino acid residues in IkappaBalpha that contact NF-kappaB only marginally affects complex binding affinity, indicating a lack of hot spots in NF-kappaB/IkappaBalpha complex formation. Conversion of the weak binding NF-kappaB p50 homodimer into a high affinity binding partner of IkappaBalpha requires transfer of both the NLS polypeptide and amino acid residues Asn202 and Ser203 from the NF-kappaB p65 subunit. Involvement of Asn202 and Ser203 in complex formation is surprising as these amino acid residues occupy solvent exposed positions at a distance of 20A from IkappaBalpha in the crystal structures. However, the same amino acid residue positions have been genetically isolated as determinants of binding specificity in a homologous system in Drosophila. X-ray crystallographic and solvent accessibility experiments suggest that these solvent-exposed amino acid residues contribute to NF-kappaB/IkappaBalpha complex formation by modulating the NF-kappaB p65 subunit NLS polypeptide.

About this Structure

1MY5 is a Single protein structure of sequence from Mus musculus. Full crystallographic information is available from OCA.

Reference

Solvent exposed non-contacting amino acids play a critical role in NF-kappaB/IkappaBalpha complex formation., Huxford T, Mishler D, Phelps CB, Huang DB, Sengchanthalangsy LL, Reeves R, Hughes CA, Komives EA, Ghosh G, J Mol Biol. 2002 Dec 6;324(4):587-97. PMID:12460563

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