Bacterial lipoprotein maturation

Bacterial lipoprotein maturation begins with Lgt transfer of a diacylglyceryl group to a lipobox cysteine and LspA removal of the signal peptide. The resulting diacylglyceryl lipoprotein may remain unmodified at its amino terminus or undergo lineage- and substrate-dependent tailoring: Lnt, Lnb or a compatible LnsAB complex adds a third long acyl chain; Lit relocates an existing chain to form a two-chain lyso-lipoprotein; LhaT transfers a lipid-carried acetyl group. These are distinct product routes, not interchangeable definitions of maturation. The bacterial occurrence envelope includes exemplars from Pseudomonadota, Bacillota and Bacteroidota; it does not assert universal enzyme presence or essentiality. Precursor export, lipid-donor synthesis, Lol trafficking and client functions are outside the boundary.

The required core is Lgt followed by LspA. Optional terminal routes describe capacity for a specified product; absence of one route does not negate the shared core, and presence of one does not establish the others. Multiple routes may occur across a repertoire without asserting that they act sequentially on the same substrate. Taxonomy and family membership guide investigation but do not prove activity, compatible complex assembly, donor identity or essentiality. LnsAB requires a functional A/B pair; the S. aureus pair is the explicit module exemplar. S. epidermidis pairing controls are documented separately with verified RefSeq/UniParc identities because the corresponding UniProt records are deleted. No PANTHER ancestor is invented for Lnb, LnsAB or Lit. LhaT carrier synthesis is the separate bacterial_heptaprenylglyceryl_ether_lipid module; the uncharacterized transmembrane carrier-supply mechanism is not filled with a guessed enzyme. LspA uses the current signal peptidase activity GO:0009003; its aspartic mechanism remains supported in gene/family reviews. Primary evidence corrects older review assumptions about Lnt universality and unknown monoderm N-modification. Computational scope: the generic Boolean compiler treats the LnsAB complex annoton as one activity atom and does not itself descend active_units. Family- and member-aware capacity analysis must additionally enforce both compatible partners, product chemistry and donor availability; a bare GO:0016747 match is insufficient. Panel scope: ECOLI and PSEPK have reviewed Lgt/LspA/Lnt panels, and BACSU has reviewed Lgt/LspA/LhaT. Bacteroides, S. aureus and B. cereus terminal exemplars characterize those reactions without constituting complete native upstream gene panels; B. fragilis rescue in E. coli is an engineered context. Terminal process contexts distinguish direct chemical modification from synthesis of a triacyl product: Lnt, Lnb and LnsAB carry both lipoprotein biosynthesis and modification; Lit modifies the substrate without adding a third acyl chain; LhaT acetylates the N terminus of an already lipidated protein and carries both acetylation and lipoprotein modification. These are module-level step contexts, not requests for redundant gene annotation rows. LhaT selects exact P54392; its verified family membership remains descriptive because reaction scope across PTHR40042 is unresolved.