double-psi beta-barrel fold of membrane-bound lytic murein transglycosylase A (MltA) and similar proteins
MltA, also called murein hydrolase A, is a murein-degrading enzyme that may play a role in the recycling of muropeptides during cell elongation and/or cell division. It degrades murein glycan strands and insoluble, high-molecular weight murein sacculi. Bacterial lytic transglycosylases (LTs) are classified into 4 families: family 1 includes slt70 MltC-MltF, family 2 includes MltA, family 3 includes MltB, and family 4 includes proteins of bacteriophage origin. MltA is distinct from other bacterial LTs, which are similar in structure and sequence with a lysozyme-like fold. MltA is a kidney bean-shaped monomeric protein comprised of two domains separated by a large groove, where the peptidoglycan strand binds. Domain A is made up of an N-terminal and a C-terminal portion, which corresponds to a double-psi beta-barrel (DPBB) fold. Domain B also has a beta-barrel fold topology, but it is inserted within the linear sequence of domain A. This model corresponds to the DPBB fold that consists of two interlocked "psi-structure" motifs related by a pseudo-2-fold axis. It is involved in substrate binding and catalysis.
Jiyao W et al.(2023). "The conserved domain database in 2023.",