Expression of the Peptidoglycan Recognition Protein, PGRP, in the Lactating Mammary Gland

Abstract

The peptidoglycan recognition protein, PGRP, known as an intracellular component of neutrophils, has been isolated from camel (Camelus dromedarius) milk by acid precipitation followed by heparin-sepharose affinity chromatography of the supernatant. The mean concentration in milk was about 120 mg/L. It decreased during lactation by 19% and increased in the event of severe mastitis by 45%. The protein bound to lactic acid bacteria and other gram-positive bacteria with an affinity similar to that reported for the human and murine orthologs, although the isoelectric point of the molecule was distinctly higher at pH 9.02. The N-terminus of mature camel PGRP was determined as NH2-ArgGluAspProPro-CO2H. Calculated and measured molecular masses were both 19.1 kDa, excluding the possibility of posttranslational modifcation or binding of cation ligands. The peptide probably builds a homotrimer at high concentration. The corresponding mRNA was isolated from lactating mammary gland tissue, and 5.3 kbp of the corresponding gene was sequenced. Similarities were found to the camel lactoferrin gene with regard to sites of expression and to the region 5' upstream to the gene.

Proteomics and Deep Sequencing Comparison of Seasonally Active Venom Glands in the Platypus Reveals Novel Venom Peptides and Distinct Expression Profiles

“…PGLYRP1 is a leukocyte-secreted disulfide-linked pattern receptor that hydrolyzes bacterial cell wall peptidoglycan and exerts direct bactericidal activity against both Gram-positive and Gramnegative bacteria. PGLYRP1 expression has also been detected in another modified sweat gland, the mammary gland, suggesting PGLYRP1 was a component of the common ancestral sweat gland (31). Peptidoglycan recognition family proteins are known to play a role in wasp venoms.…”

Structural Basis of Recognition of Pathogen-associated Molecular Patterns and Inhibition of Proinflammatory Cytokines by Camel Peptidoglycan Recognition Protein

“…It is also well known that their immunological makeup with single-chain IgG molecules carries a compromised immune system. Furthermore, unlike in other species, the other supporting antibacterial proteins, such as lactoperoxidase and lysozyme C, are available only at very low concentrations in the mammary secretions of camels (10). Therefore, these very useful properties of CPGRP-S may be of great therapeutic value as an antibiotic to protect mammary glands and newborns from bacterial infection.…”

“…The PGRPs are highly conserved protein molecules that may detect PAMPs from either Gram-negative or Gram-positive bacteria or both. The short form of PGRP isolated from the secretions of camel mammary glands (CPGRP-S) has been found to act potently against both Gram-negative and Gram-positive bacteria (10). We report here binding studies performed with CPGRP-S and two commonly occurring PAMPs, LPS and LTA, as well as detailed analyses of the three-dimensional structures of the two complexes of CPGRP-S with LPS (structure X) and with LTA (structure Y) determined at high resolutions.…”

Camel Milk: An Important Natural Adjuvant

“…Of the two major whey proteins, a-lactalbumin is the main component in camel milk, while b-lactoglobulin is deficient [67]. Other whey proteins present in camel milk are serum albumin, lactoferrin, immunoglobulins and peptidoglycan recognition protein [56]. The ratio of whey protein to casein is higher in camel milk than in cow milk.…”