Peptidoglycan recognition protein-SD provides versatility of receptor formation in Drosophila immunity

doi:10.1073/pnas.0710092105

Peptidoglycan recognition protein-SD provides versatility of receptor formation in Drosophila immunity

*Genetics Unit, Department of Biochemistry, South Parks Road, University of Oxford, Oxford OX1 3QU, United Kingdom;
^†Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford OX3 7BN, United Kingdom;
^‡Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, 2781-901 Oeiras, Portugal; and
^§Department of Biochemistry, University of Cambridge, Cambridge CB2 1GA, United Kingdom

Edited by Fotis C. Kafatos, Imperial College London, London, United Kingdom, and approved June 3, 2008 (received for review October 23, 2007)

Abstract

In Drosophila, the enzymatic activity of the glucan binding protein GNBP1 is needed to present Gram-positive peptidoglycan (PG) to peptidoglycan recognition protein SA (PGRP-SA). However, an additional PGRP (PGRP-SD) has been proposed to play a partially redundant role with GNBP1 and PGRP-SA. To reconcile the genetic results with events at the molecular level, we investigated how PGRP-SD participates in the sensing of Gram-positive bacteria. PGRP-SD enhanced the binding of GNBP1 to Gram-positive PG. PGRP-SD interacted with GNBP1 and enhanced the interaction between GNBP1 and PGRP-SA. A complex containing all three proteins could be detected in native gels in the presence of PG. In solution, addition of a highly purified PG fragment induced the occurrence not only of the ternary complex but also of dimeric subcomplexes. These results indicate that the interplay between the binding affinities of different PGRPs provides sufficient flexibility for the recognition of the highly diverse Gram-positive PG.

Footnotes

^¶To whom correspondence should be addressed. E-mail: petros.ligoxygakis{at}bioch.ox.ac.uk
Author contributions: L.W. and P.L. designed research; L.W. performed research; R.J.C.G., M.L.A., S.R.F., and N.J.G. contributed new reagents/analytic tools; L.W., R.J.C.G., S.R.F., N.J.G., and P.L. analyzed data; and L.W., N.J.G., and P.L. wrote the paper.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission.
This article contains supporting information online at www.pnas.org/cgi/content/full/0710092105/DCSupplemental.