PDBsum entry 3nau

Transcription

PDB id: 3nau

Contents

Protein chains

56 a.a. *

Ligands

SO4

Waters ×24

* Residue conservation analysis

PDB id:

3nau

Name:

Transcription

Title:

Crystal structure of zhx2 hd2 (zinc-fingers and homeoboxes protein 2, homeodomain 2)

Structure:

Zinc fingers and homeoboxes protein 2. Chain: a, b. Fragment: hd2 domain, homeobox 2, residues 444-501. Synonym: zhx2, zinc finger and homeodomain protein 2, alpha- fetoprotein regulator 1, afp regulator 1, regulator of afp. Engineered: yes

Source:

Homo sapiens. Human. Organism_taxid: 9606. Gene: zhx2. Expressed in: escherichia coli. Expression_system_taxid: 562.

Resolution:

2.70Å R-factor: 0.207 R-free: 0.267

Authors:

J.Ren,L.E.Bird,R.J.Owens,D.K.Stammers,Oxford Protein Production Facility (Oppf)

Key ref:

L.E.Bird et al. (2010). Novel structural features in two ZHX homeodomains derived from a systematic study of single and multiple domains. Bmc Struct Biol, 10, 13-13. PubMed id: 20509910

Date:

02-Jun-10 Release date: 07-Jul-10

Protein chains

Q9Y6X8  (ZHX2_HUMAN) -  Zinc fingers and homeoboxes protein 2 from Homo sapiens

Seq: 837 a.a.

Struc: 56 a.a.

Bmc Struct Biol 10:13-13 (2010)

PubMed id: 20509910

Novel structural features in two ZHX homeodomains derived from a systematic study of single and multiple domains.

L.E.Bird, J.Ren, J.E.Nettleship, G.E.Folkers, R.J.Owens, D.K.Stammers.

ABSTRACT

BACKGROUND: Zhx1 to 3 (zinc-fingers and homeoboxes) form a set of paralogous genes encoding multi-domain proteins. ZHX proteins consist of two zinc fingers followed by five homeodomains. ZHXs have biological roles in cell cycle control by acting as co-repressors of the transcriptional regulator Nuclear Factor Y. As part of a structural genomics project we have expressed single and multi-domain fragments of the different human ZHX genes for use in structure determination. RESULTS: A total of 30 single and multiple domain ZHX1-3 constructs selected from bioinformatics protocols were screened for soluble expression in E. coli using high throughput methodologies. Two homeodomains were crystallized leading to structures for ZHX1 HD4 and ZHX2 HD2. ZHX1 HD4, although closest matched to homeodomains from 'homez' and 'engrailed', showed structural differences, notably an additional C-terminal helix (helix V) which wrapped over helix I thereby making extensive contacts. Although ZHX2 HD2-3 was successfully expressed and purified, proteolysis occurred during crystallization yielding crystals of just HD2. The structure of ZHX2 HD2 showed an unusual open conformation with helix I undergoing 'domain-swapping' to form a homodimer. CONCLUSIONS: Although multiple-domain constructs of ZHX1 selected by bioinformatics studies could be expressed solubly, only single homeodomains yielded crystals. The crystal structure of ZHX1 HD4 showed additional hydrophobic interactions relative to many known homeodomains via extensive contacts formed by the novel C-terminal helix V with, in particular, helix I. Additionally, the replacement of some charged covariant residues (which are commonly observed to form salt bridges in non-homeotherms such as the Drosophila 'engrailed' homeodomain), by apolar residues further increases hydrophobic contacts within ZHX1 HD4, and potentially stability, relative to engrailed homeodomain. ZHX1 HD4 helix V points away from the normally observed DNA major groove binding site on homeodomains and thus would not obstruct the putative binding of nucleic acid. In contrast, for ZHX2 HD2 the observed altered conformation involving rearrangement of helix I, relative to the canonical homeodomain fold, disrupts the normal DNA binding site, although protein-protein binding is possible as observed in homodimer formation.