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Solution structural model of the complex of the binding regions of human plasminogen with its M-protein receptor from

Yue Yuan1, Yetunde A Ayinuola1, Damini Singh1

  • 1W.M. Keck Center for Transgene Research, University of Notre Dame, Notre Dame, IN 46556, USA.

Journal of Structural Biology
|July 14, 2019
PubMed

Insights

Streptococcal pyogenes M-protein (PAM) A-domain peptide VEK50 binds human plasminogen (hPg) via two sites. This study reveals the structure of VEK50 complexed with hPg

Area of Science:

  • Biochemistry
  • Structural Biology
  • Microbiology

Background:

  • Streptococcal pyogenes utilizes surface M-protein (PAM) to bind human plasminogen (hPg), a crucial virulence factor.
  • The PAM A-domain is responsible for high-affinity hPg binding.
  • Understanding the molecular basis of this interaction is key to deciphering S. pyogenes pathogenesis.

Purpose of the Study:

  • To elucidate the high-resolution structure of the interaction between the PAM A-domain peptide (VEK50) and the hPg kringle 2 domain (K2hPg).
  • To identify and characterize the specific binding sites within VEK50 for K2hPg.
  • To provide structural insights into the PAM-hPg complex formation.

Main Methods:

  • High-resolution Nuclear Magnetic Resonance (NMR) spectroscopy was employed.
  • Isotopically labeled peptides (13C and 15N) were used for structure determination.
  • Mutant peptides (VEK50[RH1/AA] and VEK50[RH2/AA]) were designed to probe individual binding sites.

Main Results:

  • VEK50 possesses two distinct high-affinity binding sites for K2hPg within its A-domain, located in the a1- (RH1) and a2- (RH2) repeats.
  • NMR-derived solution structures show that VEK50 can bind two K2hPg molecules simultaneously, positioned close to each other.
  • The binding affinities for the two sites are slightly different.

Conclusions:

  • The PAM A-domain acts as a scaffold capable of accommodating two K2hPg molecules.
  • This bivalent binding mechanism provides a structural basis for the interaction between PAM and hPg.
  • The findings offer critical insights into a key virulence mechanism of Streptococcus pyogenes.
Keywords:
3-D solution structureA-repeatsBacterial receptorModular proteinsNMR structuresPeptide mutagenesisPlasminogen binding

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