LRP chaperone MESD (also known as mesoderm development candidate 2) represents a set of highly conserved proteins found from nematodes to humans. It is a chaperone that specifically assists with the folding of β-propeller/EGF modules within the family of low-density lipoprotein receptors (LDLRs). It also acts as a modulator of the Wnt pathway, since some LDLRs are coreceptors for the canonical Wnt pathway and is essential for specification of embryonic polarity and mesoderm induction []. The Drosophila homologue, known as boca, is an endoplasmic reticulum protein required for wingless signaling and trafficking of LDL receptor family members [].The final C-terminal residues, KEDL, are the endoplasmic reticulum retention sequence as it is an ER protein specifically required for the intracellular trafficking of members of the low-density lipoprotein family of receptors (LDLRs) []. The N- and C-terminal sequences are predicted to adopt a random coil conformation, with the exception of an isolated predicted helix within the N-terminal region, The central folded domain flanked by natively unstructured regions is the necessary structure for facilitating maturation of LRP6 (Low-Density Lipoprotein Receptor-Related Protein 6 Maturation) [].
This family represents the putative oxygenase component of the oxygen-dependent methionine synthase MesD, called MesX, present in aerobic bacteria []. MesX is required for MesD for its activity. MesD/MesX has the advantage of not requiring cobalamin for methionine synthesis.
Bacteriocins are antibacterial proteinaceous compounds produced by bacteria. In Gram-positive bacteria, they are divided into four classes. Within the class II, constituted by non-modified peptides produced mainly by lactic acid bacteria, bacteriocins of the subclass IIa (also known as pediocin-like bacteriocins), such as mesentericin Y105, are of particular interest. They are active against the foodborne pathogen Listeria monocytogenes and share a similar primary structure, with a conserved N-terminal motif (YGNGV). Subclass IIa bacteriocins induce membrane permeabilization of sensitive strains []. Class-IId contains the one-peptide non-cyclic bacteriocins that show no sequence similarity to the pediocin-like bacteriocins, and include lactococcin A (LcnA) [].The translocation of most of the class II bacteriocins requires a type I secretion system which is composed of maturation and secretion protein and an accessory factor. MesD and MesE encode the dedicated transport system of mesentericin Y105 []. Secretion and maturation of LcnA depends on the two membrane proteins LcnC and LcnD []. This family consist of accessory factors such as MesE and LcnD. Their function remains unclear, but they are required for full production of these bacteriocins [, ].
