PDBsum entry 4eot

Transcription/DNA

PDB id: 4eot

Contents

Protein chains

92 a.a.

DNA/RNA

Ligands

SO4 ×3

Waters ×4

PDB id:

4eot

Name:

Transcription/DNA

Title:

Crystal structure of the mafa homodimer bound to the consensus mare

Structure:

Transcription factor mafa. Chain: a, b. Fragment: DNA-binding domain (unp residues 226-318). Synonym: pancreatic beta-cell-specific transcriptional activator, transcription factor ripe3b1, v-maf musculoaponeurotic fibrosarcoma oncogene homolog a. Engineered: yes. 5'-d( Cp Cp Gp Gp Tp Gp Cp Tp Gp Ap Gp Tp Cp Ap Gp Cp Ap Gp G)-3'.

Source:

Homo sapiens. Human. Organism_taxid: 9606. Gene: mafa. Expressed in: escherichia coli. Expression_system_taxid: 562. Synthetic: yes. Synthetic: yes

Resolution:

2.86Å R-factor: 0.223 R-free: 0.260

Authors:

X.Lu,G.Guanga,C.Wan,R.B.Rose

Key ref:

X.Lu et al. (2012). A novel DNA binding mechanism for maf basic region-leucine zipper factors inferred from a MafA-DNA complex structure and binding specificities. Biochemistry, 51, 9706-9717. PubMed id: 23148532

Date:

15-Apr-12 Release date: 28-Nov-12

Protein chains

Q8NHW3  (MAFA_HUMAN) -  Transcription factor MafA from Homo sapiens

Seq: 353 a.a.

Struc: 92 a.a.

DNA/RNA chains

C-C-G-G-T-G-C-T-G-A-G-T-C-A-G-C-A-G-G 19 bases

C-C-C-T-G-C-T-G-A-C-T-C-A-G-C-A-C-C-G 19 bases

Biochemistry 51:9706-9717 (2012)

PubMed id: 23148532

A novel DNA binding mechanism for maf basic region-leucine zipper factors inferred from a MafA-DNA complex structure and binding specificities.

X.Lu, G.P.Guanga, C.Wan, R.B.Rose.

ABSTRACT

MafA is a proto-oncoprotein and is critical for insulin gene expression in pancreatic β-cells. Maf proteins belong to the AP1 superfamily of basic region-leucine zipper (bZIP) transcription factors. Residues in the basic helix and an ancillary N-terminal domain, the Extended Homology Region (EHR), endow maf proteins with unique DNA binding properties: binding a 13 bp consensus site consisting of a core AP1 site (TGACTCA) flanked by TGC sequences and binding DNA stably as monomers. To further characterize maf DNA binding, we determined the structure of a MafA-DNA complex. MafA forms base-specific hydrogen bonds with the flanking G(-5)C(-4) and central C(0)/G(0) bases, but not with the core-TGA bases. However, in vitro binding studies utilizing a pulse-chase electrophoretic mobility shift assay protocol revealed that mutating either the core-TGA or flanking-TGC bases dramatically increases the binding off rate. Comparing the known maf structures, we propose that DNA binding specificity results from positioning the basic helix through unique phosphate contacts. The EHR does not contact DNA directly but stabilizes DNA binding by contacting the basic helix. Collectively, these results suggest a novel multistep DNA binding process involving a conformational change from contacting the core-TGA to contacting the flanking-TGC bases.