Exocellular Protein Research Articles

Purification and characterization of exocellular proteases produced by a clinical isolate and a laboratory strain of Pseudomonas aeruginosa.

Exocellular protease production was examined in two separate strains of Pseudomonas aeruginosa, one a clinical isolate and the other a laboratory strain. Both strains produced two separate proteases (proteases 1 and 2) which were indistinguishable from one strain to the other. The two proteases were purified by a two-step procedure of gel filtration chromatography followed by ion-exchange chromatography. Proteases 1 and 2 were shown to be distinct serologically and unrelated by physiochemical parameters examined. Protease 1 was the major exocellular protein produced and contributed about 95% of the total protease activity of the culture. It was etimated to have a molecular weight of 34850 and was also shown to contain 10% glucosamine by weight. Protease 2, in contrast, had an estimated molecular weight of 52750 and contained no detectable carbohydrate. Proteases 1 and 2 were both stimulated by Ca2+, and Mg2+ and inhibited by Co2+Zn2+, and 1,10-o-phenanthroline. Protease 1 was also inhibited by EDTA. In addition to protease activity, both proteases 1 and 2 demonstrated elastase activity as well as a limited collagenase activity. Specificity of the two protease against synthetic peptides was, however, quite different. Protease 1, but not protease 2, showed a preference for peptide bonds in which the amino group was contributed by an amino acid with a hydrophovic R group.

Interaction of streptolysin O with sterols

A quantitative study of the specific inhibitory power of cholesterol and other sterols on the hemolytic properties of streptolysin O is reported. This streptococcal exocellular protein is a cytolytic toxin which disrupts cytoplasmic membranes of eukaryote cells. The structural characteristics, particularly the stereochemical ones required for a steroid molecule to inhibit the cytolytic activity of streptolysin O, have been investigated in detail. By immunodiffusion techniques, in agar gel plates or tubes containing sterols, the formation of hydrophobic complexes between streptolysin O and inhibitory steroids, but not non-inhibitory steroids except lanosterol, is shown. Upon interaction with inhibitory steroids streptolysin O loses its immunoreactive properties towards neutralizing and precipitating homologous antibodies. An interpretation of the mechanism of biomembrane disorganization by streptolysin O is discussed in the light of its steroid binding properties.

Selective effect of pH on the production of exocellular protein by Clostridium perfringens type D.

Selective effect of pH on the production of exocellular protein by Clostridium perfringens type D.

Incorporation of C14 from amino acids and peptides into protein by Clostridium perfringens type D.

Hauschild, Andreas H. W. (University of Toronto, Toronto, Ontario, Canada). Incorporation of C(14) from amino acids and peptides into protein by Clostridium perfringens type D. J. Bacteriol. 90:1569-1574. 1965.-Uptake of C(14) from C(14)-labeled amino acids and peptides by Clostridium perfringens was measured in culture media containing acid or papain hydrolysates of C(14)-labeled Chlorella protein. Between 2 and 4 hr of growth, the rate of C(14) uptake from peptides was higher than from free amino acids. Peptides extracted from cells with hot ethyl alcohol contained six to nine times more C(14) after 4 hr of growth with C(14)-labeled peptides than with C(14)-labeled amino acids. Incorporation of C(14)-labeled glycine, serine, threonine, alanine, and proline into both cellular and exocellular protein was two to five times higher when these were supplied as components of dialyzable peptides rather than as free amino acids.