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. Author manuscript; available in PMC: 2014 Sep 1.
Published in final edited form as: Mol Microbiol. 2013 Jul 29;89(5):949–962. doi: 10.1111/mmi.12323

Fig. 7. Model of ShyA-mediated sacculus enlargement.

Fig. 7

(1) New PG (colored green) is synthesized and contains ShyA-resistant 4/5 peptide bonds (shaded red, the fifth D-Ala is colored light blue). Old PG (colored blue) contains mostly ShyA-sensitive 4/4 crosslinks (shaded blue). We follow the “three for one” model proposed by Höltje (Holtje, 1998) and thus assume that three new strands are synthesized for incorporation. (2) ShyA cleaves and removes an old PG strand without affecting the bonds in new PG. Newly synthesized PG might either be already connected to the old material (as originally proposed in the three for one model) or it might be crosslinked concomitant with ShyA action. (3) Three nascent strands replace one old strand, enlarging the PG mesh.