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Structural and biochemical characterization reveals LysGH15 as an unprecedented "EF-hand-like" calcium-binding phage

Jingmin Gu1, Yingang Feng2, Xin Feng1

  • 1Key Laboratory of Zoonosis, Ministry of Education, College of Veterinary Medicine, Jilin University, Changchun, China.

Plos Pathogens
|May 17, 2014
PubMed

Insights

The staphylococcal phage lysin LysGH15 shows potent activity against MRSA. Calcium ions act as a switch, modulating the CHAP domain

Area of Science:

  • Structural biology
  • Biochemistry
  • Microbiology

Background:

  • Staphylococcal phage lysin LysGH15 exhibits broad lytic activity against methicillin-resistant Staphylococcus aureus (MRSA).
  • The molecular mechanisms underlying LysGH15's lytic activity and its domain functions remain largely uncharacterized.

Purpose of the Study:

  • To elucidate the molecular mechanism of LysGH15, focusing on its lytic activity and domain structures.
  • To investigate the role of calcium ions in LysGH15 function and characterize its unique calcium-binding site.

Main Methods:

  • X-ray crystallography was employed to determine the structures of LysGH15's individual domains.
  • Structure-guided mutagenesis and Nuclear Magnetic Resonance (NMR) spectroscopy were used to identify key residues and catalytic mechanisms.
  • Biochemical assays were performed to assess lytic activity and substrate interactions.

Main Results:

  • The crystal structure of the LysGH15 CHAP domain revealed a unique 'EF-hand-like' calcium-binding site, the first reported in the CHAP family.
  • Calcium ions were found to modulate the CHAP domain's activity, acting as a switch between active and inactive states.
  • Structure-guided mutagenesis identified essential residues and a zinc ion in the amidase-2 domain for catalysis, and key substrate-interacting residues in the SH3b domain.

Conclusions:

  • This study provides the first structural and biochemical insights into a staphylococcal phage lysin, specifically LysGH15.
  • The discovery of a calcium-binding site in the CHAP domain and its role as a regulatory switch represents a significant advancement in understanding lysin function.
  • The findings pave the way for understanding the catalytic mechanism and substrate interactions of staphylococcal phage lysins.

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