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Template:STRUCTURE 1k1b

Crystal structure of the ankyrin repeat domain of Bcl-3: a unique member of the IkappaB protein family

Overview

IkappaB proteins associate with the transcription factor NF-kappaB via their ankyrin repeat domain. Bcl-3 is an unusual IkappaB protein because it is primarily nucleoplasmic and can lead to enhanced NF-kappaB-dependent transcription, unlike the prototypical IkappaB protein IkappaBalpha, which inhibits NF-kappaB activity by retaining it in the cytoplasm. Here we report the 1.9 A crystal structure of the ankyrin repeat domain of human Bcl-3 and compare it with that of IkappaBalpha bound to NF-kappaB. The two structures are highly similar over the central ankyrin repeats but differ in the N-terminal repeat and at the C-terminus, where Bcl-3 contains a seventh repeat in place of the acidic PEST region of IkappaBalpha. Differences between the two structures suggest why Bcl-3 differs from IkappaBalpha in selectivity towards various NF-kappaB species, why Bcl-3 but not IkappaBalpha can associate with its NF-kappaB partner bound to DNA, and why two molecules of Bcl-3 but only one of IkappaBalpha can bind to its NF-kappaB partner. Comparison of the two structures thus provides an insight into the functional diversity of IkappaB proteins.

About this Structure

1K1B is a Single protein structure of sequence from Homo sapiens. Full crystallographic information is available from OCA.

Reference

Crystal structure of the ankyrin repeat domain of Bcl-3: a unique member of the IkappaB protein family., Michel F, Soler-Lopez M, Petosa C, Cramer P, Siebenlist U, Muller CW, EMBO J. 2001 Nov 15;20(22):6180-90. PMID:11707390 Page seeded by OCA on Fri May 2 22:10:28 2008