Simian virus 40 small-t antigen binds two zinc ions

Area of Science:

• Molecular biology
• Virology
• Protein biochemistry

Background:

• The simian virus 40 small-t antigen (small-t) is a viral protein.
• Protein stability is crucial for biological function.
• Zinc ions are known to play roles in protein structure and function.

Purpose of the Study:

• To investigate the role of cysteine residues in the stability of simian virus 40 small-t antigen.
• To determine the zinc-binding capacity of purified small-t protein.
• To explore potential structural similarities between small-t and other zinc-binding proteins.

Main Methods:

• Expression and purification of simian virus 40 small-t antigen in bacterial and baculovirus systems.
• In vitro assays to assess protein stability.
• Zinc-binding assays to quantify zinc ions bound per protein molecule.

Main Results:

• Six cysteine residues were identified as critical for the stability of simian virus 40 small-t.
• Purified small-t protein demonstrated the ability to bind two molecules of zinc per molecule of protein.
• The zinc-binding stoichiometry suggests a potential binuclear cluster formation.

Conclusions:

• The stability of simian virus 40 small-t antigen is dependent on six cysteine residues.
• Small-t protein binds zinc ions in vitro, indicating a role for zinc in its structure.
• The zinc-binding characteristics of small-t suggest a resemblance to GAL4's Zn(II)2Cys6 cluster.