The antibacterial peptide seminal plasmin alters permeability of the inner membrane of E. coli

Abstract

Seminal plasmin (SPLN) a 47mresiduc pcptide, isolated from bovine seminal plasma, exhibits antibacterial activity against Gram-positive and Gram-negative bacteria. Although SPLN strongly inhibits the transcription of various natural and synthetic templates by E. co/i RNA polymera~e in vitro, it also associates with model membranes of phosphatidylcholine and phosphatidic acid. We have undertaken experiments to ascertain whether SPLN pcrmcabilizes the bacterial inner membrane and rhereby exerts its antibacterial aciirity. as in thecascofrecently isolatedantibacterial pcptidcs from mammalian sources. Our results show that SPLN affects the permeability properties of the bacteria1 inner membrane which is reflected by increased uptake of onho-nitrophenylgalactoside (ONPG), which can normally be translocated only by protein transporters. SPLN has also been shown to act on the outer membrane, since divalent cations ir,hibit antibacterial activity.Seminal plasmin; Antibacterial protein; Membrane permeability: Spheroplast

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“…The shift in biocidal efficacy over time for the two species can be attributed to the differences in the cell anatomy (i.e., cell wall structure) − and bacterial stress responses − between these organisms. While thicker peptidoglycan in Gram-positive bacteria is known to provide more protection against physical stress, chemical stress from Ag + seems to dominate here .…”

“…While thicker peptidoglycan in Gram-positive bacteria is known to provide more protection against physical stress, chemical stress from Ag + seems to dominate here . Lipopolysaccharide (LPS) is only present on the Gram-negative membrane, which stabilizes the outer cell wall against constituents in water . A lack of LPS on the Gram-positive wall can substantially reduce the wall potential in the presence of divalent cations; under such conditions, the passage of Ag + across the wall is facilitated .…”

“…73 Lipopolysaccharide (LPS) is only present on the Gram-negative membrane, which stabilizes the outer cell wall against constituents in water. 68 A lack of LPS on the Gram-positive wall can substantially reduce the wall potential in the presence of divalent cations; 69 under such conditions, the passage of Ag + across the wall is facilitated. 69 Here, the divalent cation, Mg 2+ , was present in the synthetic background water at a constant concentration, whereas the Ag + concentration was initially elevated and decreased over time.…”