Targeting of muralytic enzymes to the cell division site of Gram-positive bacteria: repeat domains direct autolysin to the equatorial surface ring of Staphylococcus aureus.
Staphylococcus aureus secretes autolysin ( Atl) to complete cell division by hydrolyzing its thick cell wall layer at a designated site, known as the equatorial surface ring. Secreted pro- Atl (1256 amino acids) is cleaved at residues 198 and 775 to generate a pro-peptide, amidase and glucosaminidase, respectively. Here we examined the mechanism that directs amidase and glucosaminidase to the cell division site on the staphylococcal surface. Targeting of pro- Atl to the cell surface occurred prior to its proteolytic processing. Three repeat domains (R1, R2 and R3) located at the center of pro- Atl are necessary and sufficient for the targeting of reporter proteins to the equatorial surface ring. Pro- Atl cleavage at residue 775 separates the polypeptide such that R1 and R2 are linked to the C-terminus of amidase, whereas R3 is located at the N-terminus of glucosaminidase. Thus, it appears that the repeat domains direct pro- Atl, amidase and glucosaminidase to a specific receptor at the equatorial surface ring of staphylococci, thereby allowing localized peptidoglycan hydrolysis and separation of the dividing cells.[1]References
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