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Pilus backbone protein PitB of Streptococcus pneumoniae contains stabilizing intramolecular isopeptide bonds

Dorothea Zähner1, Ashish R Gandhi, Olga Stuchlik

  • 1Division of Infectious Diseases, Department of Medicine, Emory University School of Medicine, 1639 Pierce Dr., Suite 2101, Atlanta, GA 30322, USA. dzahner@emory.edu

Biochemical and Biophysical Research Communications
|May 24, 2011
PubMed

Insights

Streptococcus pneumoniae type 2 pili are stabilized by intramolecular isopeptide bonds in the PitB protein. These bonds enhance pilus thermal stability without affecting proteolytic resistance.

Area of Science:

  • Microbiology
  • Structural Biology
  • Biochemistry

Background:

  • Streptococcus pneumoniae type 2 pili are emerging fimbrial structures.
  • These pili are polymers of the structural protein PitB.
  • Intramolecular isopeptide bonds stabilize related pilus proteins.

Purpose of the Study:

  • To investigate the presence and function of intramolecular isopeptide bonds in PitB.
  • To determine the specific locations of these bonds within PitB.

Main Methods:

  • Tandem mass spectrometry
  • Edman sequencing
  • Analysis of mutant PitB proteins lacking isopeptide bonds.

Main Results:

  • Two intramolecular isopeptide bonds were identified in PitB: Lys(63)-Asn(214) and Lys(243)-Asn(372).
  • Mutant PitB proteins without these bonds showed reduced thermal stability (lower melting temperature).
  • Proteolytic stability was comparable between wild-type and mutant PitB proteins.

Conclusions:

  • Intramolecular isopeptide bonds play a crucial role in the thermal stabilization of pneumococcal type 2 pili.
  • These bonds contribute to the structural integrity of PitB, a key component of these pili.

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