Fig. 7.

Model for processing and activities of Cwp84 and Cwp13. SlpA, Cwp84, and Cwp13 are produced as preproteins containing signal peptides that are removed during processing by the sec system (step a). The propeptides of Cwp84 and Cwp13 are removed (step b), either by autocatalysis in the case of Cwp13 or by an unknown activity together with Cwp13 activity in the case of Cwp84, to form the active enzyme species that are incorporated into the S-layer (step c). Mature Cwp84 cleaves the SlpA precursor (step d), which results in the formation of the H/L complex (step e). Misfolded proteins are recognized by Cwp13 and are cleaved in their cell wall binding domains to prevent incorporation into the S-layer, resulting in detachment from the cell and deposition into the growth medium (step f). S-L, S-layer; PG, peptidoglycan; Mem, membrane; Cyt, cytoplasm.