A novel arrangement of zinc-binding residues and secondary structure in the C3HC4 motif of an alpha herpes virus protein family.
A highly conserved, cysteine-rich region plays a crucial role in the function of a family of regulatory proteins encoded by alpha herpes viruses. The so-called C3HC4 motif spans approximately 60 residues and has been predicted to bind zinc. This motif occurs in a number of other viral and cellular proteins, many of which appear to be involved in some aspect of the regulation of gene expression. We have cloned and expressed in bacteria a portion of immediate-early protein Vmw110 of herpes simplex virus type 1 that encompasses the C3HC4 motif, and the equivalent regions from the homologous proteins of varicella zoster virus and equine herpes virus type 1 (EHV-1). All three polypeptides were purified and found to bind zinc stably. None of the three interacted significantly with either DNA or RNA under our assay conditions. The EHV-1 domain yielded interpretable proton nuclear magnetic resonance spectra. Assignment of resonances and analysis of nuclear Overhauser effects revealed its secondary structure. Starting from the N terminus, this consists of an ordered but irregular loop, the first two strands of a triple-stranded antiparallel beta-sheet, two turns of an alpha-helix, a second irregular loop, and the third strand of the beta-sheet. It appears that, taking the cysteine and histidine residues in turn, cysteine residues I, II, IV and V co-ordinate one zinc atom while the histidine residue and cysteine residues III, VI and VII co-ordinate a second zinc atom. This arrangement of secondary structure differs from that found in other characterized zinc-containing proteins.
Everett
R D
RD
MRC Virology Unit, Institute of Virology, Glasgow, Scotland, U.K.
Barlow
P
P
Milner
A
A
Luisi
B
B
Orr
A
A
Hope
G
G
Lyon
D
D
D000595:Amino Acid Sequence; D004861:Herpesvirus 1, Equid / Q000737:chemistry*; D018259:Herpesvirus 1, Human / Q000737:chemistry*; D014645:Herpesvirus 3, Human / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008667:Metalloproteins / Q000737:chemistry*; D008969:Molecular Sequence Data; D017433:Protein Structure, Secondary; D011994:Recombinant Proteins; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D014764:Viral Proteins / Q000737:chemistry*; D015032:Zinc / Q000737:chemistry
D008667:Metalloproteins; D011994:Recombinant Proteins; D014764:Viral Proteins; D015032:Zinc