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3D domain, named for 3 conserved aspartate residues, is found in mltA-like lytic transglycosylases and numerous other contexts This family contains the 3D domain, named for its 3 conserved aspartates. It is found in conjunction with numerous other domains such as MltA (membrane-bound lytic murein transglycosylase A). These aspartates are critical active site residues of mltA-like lytic transglycosylases. Escherichia coli peptidoglycan lytic transglycosylase (LT) initiates cell wall recycling in response to damage, during bacterial fission, and cleaves peptidoglycan (PG) to create functional spaces in its wall. MltA has 2 domains, separated by a large groove, where the peptidoglycan strand binds. The C-terminus has a double-psi beta barrel fold within the 3D domain, which forms the larger A domain along with the N-terminal region of Mlts, but is also found in various other domain architectures. Peptigoglycan (also known as murein) chains, the primary structural component of bacterial cells walls, are comprised of alternating beta-1-4-linked N-acetylmuramic acid (MurNAc) and N-acetyl-D-glucosamine (GlcNAc); lytic transglycosylases (LTs) cleave this beta-1-4 bond. Typically, LTs are exolytic, releasing Metabolite 1 (GlcNAc-anhMurNAc-L-Ala-D-Glu-m-Dap-D-Ala-D-Ala) from the ends of the PG strands. In contrast, membrane-bound lytic murein transglycosylase E (MltE) is endolytic , cleaving in the middle of PG strands, with further processing to Metabolite 1 accomplished by other LTs. In E. coli, there are six membrane- bound LTs: MltA-MltF and soluble Slt70. Slt35 is a soluble fragment cleaved from MltB. Bacterial LTs are classified in 4 families: Family 1 includes slt70 MltC-MltF, Family 2 includes MltA, Family 3 includes MltB, and family 4 of bacteriophage origin. While most LTs are related members of the lysozyme-like lytic transglycosylase family, MltA represents a distinct fold and sequence conservation. |
Jiyao W et al.(2023). "The conserved domain database in 2023.",