A high-affinity metal-binding peptide from Escherichia coli HypB.

Area of Science:

• Biochemistry
• Structural Biology
• Microbiology

Background:

• The [NiFe]-hydrogenase enzyme is crucial for energy metabolism in many microorganisms.
• Accessory proteins like HypB are essential for the maturation of [NiFe]-hydrogenase.
• Understanding nickel-binding mechanisms in HypB is key to elucidating hydrogenase assembly.

Purpose of the Study:

• To identify and characterize the high-affinity nickel-binding site of the Escherichia coli HypB protein.
• To determine the structural and functional significance of the N-terminal region of HypB in nickel binding.

Main Methods:

• Site-directed mutagenesis was employed to probe the function of specific residues.
• Metal-binding fusion protein analysis was used to study nickel coordination.
• Density Functional Theory (DFT) calculations provided insights into the electronic structure of the nickel-binding site.

Main Results:

• The high-affinity nickel-binding site was localized to the N-terminus of HypB.
• The N-terminal amine and three cysteine residues within a CXXCGCXXX motif were identified as key ligands.
• A synthesized peptide containing this sequence bound nickel with comparable affinity and structure to the native protein.

Conclusions:

• The N-terminal sequence of HypB is a self-sufficient, high-affinity nickel-binding motif.
• This finding simplifies the understanding of nickel insertion into [NiFe]-hydrogenase.
• The identified motif could be a target for future protein engineering or therapeutic strategies.