PROSITE documentation PDOC00713

Prokaryotic transglycosylases signature

Bacterial lytic transglycosylases degrade murein via cleavage of the β-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. Escherichia coli has at least three different lytic transglycosylases: two soluble isozymes of 65 Kd and 35 Kd and a membrane-bound enzyme of 38 Kd. The sequence of the 65 Kd enzyme (gene slt) has been determined [1]. A domain of about 90 residues located near the C-terminal section of slt was recently shown [2] to be present in a number of other prokaryotic and phage proteins:

• Membrane-bound lytic murein transglycosylase C (gene mltC).
• Membrane-bound lytic murein transglycosylase D (gene mltD).
• Membrane-bound lytic murein transglycosylase E (gene mltE).
• Phage T7 internal protein D which may be involved in the lysis of the bacterial cell wall during the release of phage progeny.
• Phage PRD1 gene 7 protein.
• Alteromonas strain M-1 possible tributyltin chloride resistance protein.
• Escherichia coli hypothetical protein yfhD.

The domain shared by these proteins could be involved in catalytic activity. The most conserved part of this domain is its N-terminal extremity which we used as a signature pattern. It contains two conserved serines and a glutamate which has been shown [3] to be involved in the catalytic mechanism.