Induction of autolysis in starved Escherichia coli cells by seminalplasmin, an antimicrobial protein from bovine seminal plasma

Abstract A pair of relA ⁺ and relA E. coli strains, otherwise isogenic, were studied with regard to the susceptibility of starved cells to lysis induced by the natural peptide seminalplasmin. Starved relA cells were more sensitive to seminalplasmin-induced lysis when compared to starved relA ⁺ cells. Nevertheless, pronounced lysis of starved relA ⁺ cells was observed with increase in the concentration of seminalplasmin. In conctrast, ampicillin could not lyse starved relA ⁺ cells even at very high concentrations. Further, seminalplasmin could cause loss of viability and degradation of peptidoglycan in starved relA ⁺ cells. These observations suggest that, unlike many other antibiotics, seminalplasmin can induce autolysis under the conditions of a stringent response.     

Bacteriolytic activity of seminalplasmin

Seminalplasmin, an antimicrobial protein from bovine seminal plasma, lysed both Gram-positive and Gram-negative bacteria but not Candida albicans. The lytic activity was not lysozyme-like and was not affected by inhibitors of RNA or protein synthesis or by azide; it was strongly inhibited by divalent cations like Ca2+, Mn2+ and Mg2+ at millimolar concentrations. Maximum lysis of Escherichia coli was obtained at 37 degrees C; heat treatment of E. coli drastically reduced its susceptibility to lysis by seminalplasmin. E. coli cells in the stationary phase of growth were lysed much less than those in the exponential phase, and those grown in an enriched medium were lysed much more than those grown in a minimal medium. It appears that the lytic activity of seminalplasmin is due to the activation of an autolysin.     

Identification and bioinformatic analysis of the membrane proteins of synechocystis sp. PCC 6803

Background  

The membranes of Synechocystis sp. PCC 6803 play a central role in photosynthesis, respiration and other important metabolic pathways. Comprehensive identification of the membrane proteins is of importance for a better understanding of the diverse functions of its unique membrane structures. Up to date, approximately 900 known or predicted membrane proteins, consisting 24.5% of Synechocystis sp. PCC 6803 proteome, have been indentified by large-scale proteomic studies.     

Synthesis, spectroscopic, and cytotoxicity studies of some diamine and diimine platinum(II) complexes of diethyldithiocarbamate

Four new water soluble complexes of the formula [Pt(DA)(DDTC)]NO3 (where DA is 2,2'-bipyridine, 1,10-phenanthroline, 1,2-diaminopropane, or 1,2-diaminocyclohexane, and DDTC is diethyldithiocarbamate anion) have been synthesized by reaction of platinum-diamine/diimine diaqua complex with sodium diethyldithiocarbamate in molar ratio of 1:1. These complexes have been characterized by the chemical analysis, and ultraviolet-visible, infra-red and 1H NMR spectroscopy. The infrared and 1H NMR spectral studies of these complexes have ascertained the modes of binding of diamine/diimine and diethyldithiocarbamate to platinum. The molar conductance values of these platinum complexes in conductivity water suggest them to be 1:1 electrolytes. These four complexes and two other complexes containing ethylenediamine and 1,3-diaminopropane ligands have been tested against P-388 lymphocytic leukemic cells. Out of them only 2,2'-bipyridine and 1,10-phenanthroline complexes show 1.D.50 values less than cisplatin.