PDBsum entry 2k7s

Transcription

PDB id: 2k7s

Contents

Protein chain

119 a.a. *

* Residue conservation analysis

PDB id:

2k7s

Name:

Transcription

Title:

Human arnt c-terminal pas domain, 3 residue ib slip

Structure:

Aryl hydrocarbon receptor nuclear translocator. Chain: a. Fragment: arnt pas-b. Synonym: arnt protein, dioxin receptor, nuclear translocator, hypoxia-inducible factor 1 beta, hif-1 beta. Engineered: yes. Mutation: yes

Source:

Homo sapiens. Human. Organism_taxid: 9606. Gene: arnt. Expressed in: escherichia coli. Expression_system_taxid: 562.

NMR struc:

20 models

Authors:

M.R.Evans,P.B.Card,K.H.Gardner

Key ref:

M.R.Evans et al. (2009). ARNT PAS-B has a fragile native state structure with an alternative beta-sheet register nearby in sequence space. Proc Natl Acad Sci U S A, 106, 2617-2622. PubMed id: 19196990 DOI: 10.1073/pnas.0808270106

Date:

20-Aug-08 Release date: 20-Jan-09

Protein chain

P27540  (ARNT_HUMAN) -  Aryl hydrocarbon receptor nuclear translocator from Homo sapiens

Seq: 789 a.a.

Struc: 119 a.a.*

* PDB and UniProt seqs differ at 6 residue positions (black crosses)

Enzyme reactions

• Enzyme class: E.C.?

DOI no: 10.1073/pnas.0808270106

Proc Natl Acad Sci U S A 106:2617-2622 (2009)

PubMed id: 19196990

ARNT PAS-B has a fragile native state structure with an alternative beta-sheet register nearby in sequence space.

M.R.Evans, P.B.Card, K.H.Gardner.

ABSTRACT

The aryl hydrocarbon receptor nuclear translocator (ARNT) is a basic helix-loop-helix Period/ARNT/Single-minded (bHLH-PAS) protein that controls various biological pathways as part of dimeric transcriptional regulator complexes with other bHLH-PAS proteins. The two PAS domains within ARNT, PAS-A and PAS-B, are essential for the formation of these complexes because they mediate protein-protein interactions via residues located on their beta-sheet surfaces. While investigating the importance of residues in ARNT PAS-B involved in these interactions, we uncovered a point mutation (Y456T) on the solvent-exposed beta-sheet surface that allowed this domain to interconvert with a second, stable conformation. Although both conformations are present in equivalent quantities in the Y456T mutant, this can be shifted almost completely to either end point by additional mutations. A high-resolution solution structure of a mutant ARNT PAS-B domain stabilized in the new conformation revealed a 3-residue slip in register and accompanying inversion of the central Ibeta-strand. We have demonstrated that the new conformation has >100-fold lower in vitro affinity for its heterodimerization partner, hypoxia-inducible factor 2alpha PAS-B. We speculate that the pliability in beta-strand register is related to the flexibility required of ARNT to bind to several partners and, more broadly, to the abilities of some PAS domains to regulate their activities in response to small-molecule cofactors.

Selected figure(s)

Figure 2.
ARNT PAS-B can exist in two distinct conformations. (A) Widespread peak doubling is observed throughout ^15N-^1H HSQC spectra of Y456T ARNT PAS-B, as seen by comparison with spectra from the wild-type protein. Several doubled sites are highlighted with blue circles in the Y456T spectrum. (B) The E403 resonance from the Y456T ARNT mutant indicates two slowly exchanging conformations, but the relative populations of these can be perturbed by additional mutations. (C) Demonstration that conformations 1 and 2 are in equilibrium is provided by Mono Q separation of conformation 2 from a Y456T sample and monitoring the reestablishment of the equilibrium with extended incubation.

Figure 5.
Residues adopt a similar conformation in both structures. (A and B) Sequence (A) and structure (B) alignment of both mutant and wild-type Iβ strands. Shifted side chains adopt conformations of wild-type residues despite changes in identity or sequence. This is clearly seen by residue C459, where in the wild-type conformation it is buried in the core but in the mutant conformation, it slips 3 residues, becoming solvent-exposed and filling the space occupied by T462.

Figures were selected by the author.