Expression, purification and crystallization of a membrane-associated, catalytically active type I signal peptidase from Staphylococcus aureus

Acta Crystallogr F Struct Biol Commun. 2015 Jan 1;71(Pt 1):61-5. doi: 10.1107/S2053230X1402603X. Epub 2015 Jan 1.


Staphylococcus aureus infections are becoming increasingly difficult to treat as they rapidly develop resistance to existing antibiotics. Bacterial type I signal peptidases are membrane-associated, cell-surface serine proteases with a unique catalytic mechanism that differs from that of eukaryotic endoplasmic reticulum signal peptidases. They are thus potential antimicrobial targets. S. aureus has a catalytically active type I signal peptidase, SpsB, that is essential for cell viability. To elucidate its structure, the spsB gene from S. aureus Newman strain was cloned and overexpressed in Escherichia coli. After exploring many different protein-modification constructs, SpsB was expressed as a fusion protein with maltose-binding protein and crystallized by hanging-drop vapour diffusion. The crystals belonged to the monoclinic space group P2(1) and diffracted to 2.05 Å resolution. The crystal structure of SpsB is anticipated to provide structural insight into Gram-positive signal peptidases and to aid in the development of antibacterial agents that target type I signal peptidases.

Keywords: SpsB; Staphylococcus aureus; cell secretion; maltose-binding fusion protein; type I signal peptidase.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Substitution
  • Bacterial Proteins / biosynthesis
  • Bacterial Proteins / chemistry*
  • Bacterial Proteins / isolation & purification
  • Crystallization
  • Crystallography, X-Ray
  • Maltose-Binding Proteins / biosynthesis
  • Maltose-Binding Proteins / chemistry
  • Maltose-Binding Proteins / isolation & purification
  • Membrane Proteins / biosynthesis
  • Membrane Proteins / chemistry*
  • Membrane Proteins / isolation & purification
  • Recombinant Fusion Proteins / biosynthesis
  • Recombinant Fusion Proteins / chemistry
  • Recombinant Fusion Proteins / isolation & purification
  • Serine Endopeptidases / biosynthesis
  • Serine Endopeptidases / chemistry*
  • Serine Endopeptidases / isolation & purification
  • Staphylococcus aureus / enzymology*


  • Bacterial Proteins
  • Maltose-Binding Proteins
  • Membrane Proteins
  • Recombinant Fusion Proteins
  • Serine Endopeptidases
  • type I signal peptidase