InterPro: IPR008258 Lytic transglycosylase-like, catalytic

Bacterial lytic transglycosylases degrade murein via cleavage of the beta-1,4-glycosidic bond between N-acetylmuramic acid and N-acetylglucosamine, with the concomitant formation of a 1,6-anhydrobond in the muramic acid residue. There are both soluble (Slt enzymes) and membrane-bound (Mlt enzymes) lytic transglycosylases that differ in size, sequence, activity, specificity and location. The multi-domain structure of the 70 Kd soluble lytic transglycosylase Slt70 is known [1]. Slt70 has 3 distinct domains, each rich in alpha helices: an N-terminal superhelical U-shaped domain (U-domain; IPR008939), a superhelical linker domain (L-domain, IPR012289), and a C-terminal catalytic domain (IPR008258). Both the U- and L-domain share a similar superhelical structure. These two domains are connected, and together form a closed ring with a large central hole; the catalytic domain is packed on top of, and interacts with, this ring. The catalytic domain has a lysosome-like fold.

This entry represents the catalytic domain, which is structurally conserved in some membrane-bound lytic glycosylases and in bacteriophage transglycosylases, even though their sequences can differ considerably proteins [2]. The most conserved part of this domain is its N-terminal extremity that contains two conserved serines and a glutamate, which have been shown [3] to be involved in the catalytic mechanism. This family is distantly related to IPR001916.