Transferrins are iron binding transport proteins which can bind two Fe(3+) ions in association with the binding of an anion, usually bicarbonate. Lactotransferrin is a major iron-binding and multifunctional protein found in exocrine fluids such as breast milk and mucosal secretions. Has antimicrobial activity. Antimicrobial properties may include bacteriostasis, which is related to its ability to sequester free iron and thus inhibit microbial growth, as well as direct bactericidal properties leading to the release of lipopolysaccharides from the bacterial outer membrane. The most effective inhibitory activity is seen against E.coli and P.aeruginosa. Has anabolic, differentiating and anti-apoptotic effects on osteoblasts and can also inhibit osteoclastogenesis, possibly playing a role in the regulation of bone growth. Interferes with the lipopolysaccharide (LPS)-stimulated TLR4 signaling, but cannot directly stimulate the TLR4 signaling pathway and subsequent NF-kappa-B activation. Lactoferricin B is an antimicrobial peptide. Inhibits the growth of Gram-negative and Gram-positive bacteria. The lactotransferrin transferrin-like domain 1 functions as a serine protease of the peptidase S60 family that cuts arginine rich regions. This function contributes to the antimicrobial activity. Shows a preferential cleavage at -Arg-Ser-Arg-Arg-|- and -Arg-Arg-Ser-Arg-|-, and of Z-Phe-Arg-|-aminomethylcoumarin sites. Inhibited by PMSF and Pefabloc. Optimum pH is 7.5. Optimum temperature is 25 degrees Celsius. Monomer. Found in a complex with LTF, CLU, EPPIN and SEMG1 (By similarity). Secreted into most exocrine fluids by various endothelial cells. Stored in the secondary granules of neutrophils (By similarity). Belongs to the transferrin family.