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Updated: Aug 15, 2026
Recombinant Protein Expression, Crystallization, and Biophysical Studies of a Bacillus-conserved Nucleotide Pyrophosphorylase, BcMazG
Published on: May 16, 2017
Role of the microcin B17 propeptide in substrate recognition: solution structure and mutational analysis of McbA1-26
1Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA.
Background:
The peptide antibiotic microcin B17 (MccB17) contains oxazole and thiazole heterocycles formed by the post-translational modification of four cysteine and four serine residues. An amino-terminal propeptide targets the 69 amino acid precursor of MccB17 (preproMccB17) to the heterocyclization enzyme MccB17 synthetase. The mode of synthetase recognition has been unclear, because there has been limited structural information available on the MccB17 propeptide to date.
Results:
The solution structure of the MccB17 propeptide (McbA1-26), determined using nuclear magnetic resonance, reveals that McbA1-26 is an amphipathic alpha helix. Mutational analysis of 13 propeptide residues showed that Phe8 and Leu12 are essential residues for MccB17 synthetase recognition. A domain of the propeptide was putatively identified as the region that interacts with the synthetase.
Conclusions:
MccB17 synthetase recognizes key hydrophobic residues within a helical propeptide, allowing the selective heterocyclization of downstream cysteine and serine residues in preproMccB17. The determination of the solution structure of the propeptide should facilitate the investigation of other functions of the propeptide, including a potential role in antibiotic secretion.
Insights
The microcin B17 (MccB17) propeptide is an alpha helix that guides the MccB17 synthetase. Key hydrophobic residues in the propeptide are essential for this recognition and selective heterocyclization.
Area of Science:
- Biochemistry
- Molecular Biology
- Structural Biology
Background:
- Microcin B17 (MccB17) is a peptide antibiotic featuring oxazole and thiazole heterocycles.
- These heterocycles are formed via post-translational modification of cysteine and serine residues.
- An amino-terminal propeptide targets the MccB17 precursor to its synthetase enzyme, but the recognition mechanism was unclear due to limited structural data.
Purpose of the Study:
- To determine the solution structure of the MccB17 propeptide.
- To identify key residues and domains involved in MccB17 synthetase recognition.
- To elucidate the mechanism of propeptide-synthetase interaction.
Main Methods:
- Nuclear magnetic resonance (NMR) spectroscopy was used to determine the solution structure of the MccB17 propeptide (McbA1-26).
- Mutational analysis was performed on 13 propeptide residues to assess their role in synthetase recognition.
Main Results:
- The MccB17 propeptide (McbA1-26) adopts an amphipathic alpha-helical structure in solution.
- Mutational analysis identified phenylalanine at position 8 (Phe8) and leucine at position 12 (Leu12) as essential residues for MccB17 synthetase recognition.
- A specific domain within the propeptide was putatively identified as the interaction region with the synthetase.
Conclusions:
- MccB17 synthetase recognizes specific hydrophobic residues within the helical propeptide.
- This recognition ensures the selective heterocyclization of cysteine and serine residues in the MccB17 precursor.
- The determined propeptide structure aids in understanding its function and potential roles in antibiotic secretion.
