α2-Macroglobulin-Proteinase Complexes Protect Streptococcus pyogenes from Killing by the Antimicrobial Peptide LL-37

Patrik Nyberg,Magnus Rasmussen,Lars Björck

doi:10.1074/jbc.c400485200

Abstract

The significant human bacterial pathogen Streptococcus pyogenes expresses GRAB, a surface protein that binds alpha(2)-macroglobulin (alpha(2)M), a major proteinase inhibitor of human plasma. alpha(2)M inhibits proteolysis by trapping the proteinase, which, however, still remains proteolytically active against smaller peptides that can penetrate the alpha(2)M-proteinase complex. Here we report that SpeB, a cysteine proteinase secreted by S. pyogenes, is trapped by alpha(2)M bound to protein GRAB. As a consequence, SpeB is retained at the bacterial surface and protects S. pyogenes against killing by the antibacterial peptide LL-37.

Highlights

From the Department of Cell and Molecular Biology, Section for Clinical and Experimental Infectious Medicine, Lund University, S-22184 Lund, Sweden
We report that SpeB, a cysteine proteinase secreted by S. pyogenes, is trapped by ␣2M bound to protein GRAB
(␣2M)1 with high specificity and affinity [3]. ␣2M bound to the bacterial surface via GRAB entraps and inhibits host and S. pyogenes proteinases and thereby protects bacterial surface proteins and virulence determinants from degradation [3]

Summary

Introduction

␣2M bound to the bacterial surface via GRAB entraps and inhibits host and S. pyogenes proteinases and thereby protects bacterial surface proteins and virulence determinants from degradation [3]. Like several other secreted bacterial proteinases, SpeB degrades and inactivates LL-37 [5], one of the major human antibacterial peptides (for review, see Ref. 6).

Results

Conclusion