LPXTGtype

LPXTGtype refers to a class of Gram-positive bacterial surface proteins defined by the presence of a canonical LPXTG sorting signal near their C-terminus. These proteins are typically secreted by the Sec pathway and become anchored to the peptidoglycan layer through covalent linkage mediated by sortase enzymes.

Architecturally, LPXTGtype proteins possess an N-terminal signal peptide that directs export, a large extracellular domain that carries the protein’s functional activity (such as adhesion or enzymatic function), and a C-terminal anchor region. The anchor region includes the LPXTG motif, a short hydrophobic transmembrane segment, and a positively charged tail. The LPXTG motif is the recognition site for sortase enzymes, which cleave between the threonine and glycine residues and facilitate covalent attachment to the cell wall.

Functionally, LPXTGtype proteins often act as adhesins, enzymes, or virulence factors that mediate interactions with host tissues, components of the extracellular matrix, or other cells. Their cell wall anchoring positions functional domains on the bacterial surface, enhancing stability and accessibility to substrates or receptors.

Distribution and variation are widespread among Gram-positive genera, including Staphylococcus and Streptococcus species. While LPXTG is the most common motif, related sorting signals exist, and different sortases (such as SrtA, SrtB) can recognize variant motifs in some species.

Applications include the use of LPXTG motifs for surface display systems in biotechnology, enabling presentation of heterologous proteins on Gram-positive bacterial surfaces for research or vaccine development.

See also: sortase, LPXTG motif, cell wall–anchored proteins, Gram-positive bacteria.