PDBsum entry 4zc3

Viral protein

PDB id: 4zc3

Contents

Protein chain

57 a.a.

Waters ×25

PDB id:

4zc3

Name:

Viral protein

Title:

DNA binding domain of small terminase sf6 phage

Structure:

Terminase small subunit. Chain: a. Synonym: g1p. Engineered: yes

Source:

Bacillus phage sf6. Organism_taxid: 10773. Gene: small terminase. Expressed in: escherichia coli. Expression_system_taxid: 562.

Resolution:

1.40Å R-factor: 0.199 R-free: 0.213

Authors:

A.A.Antson,M.Chechik,H.T.Jenkins,S.J.Greive

Key ref:

S.J.Greive et al. (2016). DNA recognition for virus assembly through multiple sequence-independent interactions with a helix-turn-helix motif. Nucleic Acids Res, 44, 776-789. PubMed id: 26673721 DOI: 10.1093/nar/gkv1467

Date:

15-Apr-15 Release date: 30-Dec-15

Protein chain

P68928  (TERS_BPSF6) -  Terminase small subunit from Bacillus phage SF6

Seq: 145 a.a.

Struc: 57 a.a.

Enzyme reactions

• Enzyme class: E.C.?

DOI no: 10.1093/nar/gkv1467

Nucleic Acids Res 44:776-789 (2016)

PubMed id: 26673721

DNA recognition for virus assembly through multiple sequence-independent interactions with a helix-turn-helix motif.

S.J.Greive, H.K.Fung, M.Chechik, H.T.Jenkins, S.E.Weitzel, P.M.Aguiar, A.S.Brentnall, M.Glousieau, G.V.Gladyshev, J.R.Potts, A.A.Antson.

ABSTRACT

The helix-turn-helix (HTH) motif features frequently in protein DNA-binding assemblies. Viral pac site-targeting small terminase proteins possess an unusual architecture in which the HTH motifs are displayed in a ring, distinct from the classical HTH dimer. Here we investigate how such a circular array of HTH motifs enables specific recognition of the viral genome for initiation of DNA packaging during virus assembly. We found, by surface plasmon resonance and analytical ultracentrifugation, that individual HTH motifs of the Bacillus phage SF6 small terminase bind the packaging regions of SF6 and related SPP1 genome weakly, with little local sequence specificity. Nuclear magnetic resonance chemical shift perturbation studies with an arbitrary single-site substrate suggest that the HTH motif contacts DNA similarly to how certain HTH proteins contact DNA non-specifically. Our observations support a model where specificity is generated through conformational selection of an intrinsically bent DNA segment by a ring of HTHs which bind weakly but cooperatively. Such a system would enable viral gene regulation and control of the viral life cycle, with a minimal genome, conferring a major evolutionary advantage for SPP1-like viruses.