Sortase from Staphylococcus aureus does not contain a thiolate-imidazolium ion pair in its active site.

نویسندگان

  • Kevin M Connolly
  • Brenton T Smith
  • Rosemarie Pilpa
  • Udayar Ilangovan
  • Michael E Jung
  • Robert T Clubb
چکیده

Many surface proteins are anchored to the cell wall by the action of sortase enzymes, a recently discovered family of cysteine transpeptidases. As the surface proteins of human pathogens are frequently required for virulence, the sortase-mediated anchoring reaction represents a potential target for new anti-infective agents. It has been suggested that the sortase from Staphylococcus aureus (SrtA), may use a similar catalytic strategy as the papain cysteine proteases, holding its Cys184 side chain in an active configuration through a thiolate-imidazolium ion interaction with residue His120. To investigate the mechanism of transpeptidation, we have synthesized a peptidyl-vinyl sulfone substrate mimic that irreversibly inhibits SrtA. Through the study of the pH dependence of SrtA inhibition and NMR, we have estimated the pKas of the active site thiol (Cys184) and imidazole (His120) to be approximately 9.4 and 7.0, respectively. These measurements are inconsistent with the existence of a thiolate-imidazolium ion pair and suggest a general base catalysis mechanism during transpeptidation.

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منابع مشابه

Anchoring of surface proteins to the cell wall of Staphylococcus aureus. Cysteine 184 and histidine 120 of sortase form a thiolate-imidazolium ion pair for catalysis.

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عنوان ژورنال:
  • The Journal of biological chemistry

دوره 278 36  شماره 

صفحات  -

تاریخ انتشار 2003