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The leader peptide is essential for the post-translational modification of the DNA-gyrase inhibitor microcin B17

L L Madison1, E I Vivas, Y M Li

  • 1Department of Molecular Genetics and Microbiology, Harvard Medical School, Boston, Massachusetts 02115, USA.

Molecular Microbiology
|January 1, 1997
PubMed

Insights

The N-terminal leader of pre-microcin B17 (preMccB17) is crucial for its maturation into proMccB17. This leader sequence is essential for post-translational modification into the DNA-gyrase inhibitor MccB17.

Area of Science:

  • Microbiology
  • Molecular Biology
  • Biochemistry

Background:

  • Microcin B17 (MccB17) is a ribosomally synthesized antibiotic that inhibits DNA gyrase.
  • Ribosomally encoded antibiotics are synthesized as precursors with a leader peptide that is removed during maturation.
  • The biosynthesis of MccB17 involves precursor modification by McbB, McbC, and McbD enzymes.

Purpose of the Study:

  • To investigate the role of the N-terminal leader sequence of preMccB17 in its post-translational modification.
  • To determine if the leader sequence is essential for the enzymatic conversion of preMccB17 into proMccB17.

Main Methods:

  • Utilized a modification-specific antibody to track MccB17 processing, bypassing antimicrobial activity assays.
  • Constructed and analyzed preMccB17 variants lacking the leader sequence, including a preMccB17-beta-galactosidase fusion protein.

Main Results:

  • The 26-amino-acid N-terminal leader of preMccB17 was demonstrated to be essential for the conversion to proMccB17.
  • PreMccB17 peptides lacking the leader sequence, or fused to beta-galactosidase without the leader, did not undergo post-translational modification.
  • The leader sequence is indispensable for the enzymatic modification of glycine, cysteine, and serine residues into thiazole and oxazole rings.

Conclusions:

  • The N-terminal leader sequence of preMccB17 is a critical determinant for its proper post-translational modification and maturation.
  • The leader peptide acts as a recognition or guiding element for the modifying enzymes McbB, McbC, and McbD.
  • Understanding the leader's role provides insights into the biosynthesis of complex ribosomally encoded peptide antibiotics.

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