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The virulence factor CBP is the most abundant protein secreted by Histoplasma capsulatum, a pathogenic fungus that causes histoplasmosis. Although the biochemical function and pathogenic mechanism of CBP are unknown, quantitative Ca (2+) binding measurements indicate that CBP has a strong affinity for calcium ( K D = 6.45 +/- 0.4 nM). However, no change in structure was observed upon binding of calcium, prompting a more thorough investigation of the molecular properties of CBP with respect to self-association, secondary structure, and stability. Over a wide range of pH values and salt concentrations, CBP exists predominantly as a stable, noncovalent homodimer in both its calcium-free and -bound states. Solution-state NMR and circular dichroism (CD) measurements indicated that the protein is largely alpha-helical, and its secondary structure content changes little over the range of pH values encountered physiologically. ESI-MS revealed that the six cysteine residues of CBP are involved in three intramolecular disulfide bonds that help maintain a highly protease resistant structure. Thermally and chemically induced denaturation studies indicated that unfolding of disulfide-intact CBP is reversible and provided quantitative measurements of protein stability. This disulfide-linked, protease resistant, homodimeric alpha-helical structure of CBP is likely to be advantageous for a virulence factor that must survive the harsh environment within the phagolysosomes of host macrophages.

Crown ether-based synthetic cation conducting channels called hydraphiles show clear ionophoretic activity in phospholipid vesicles. These compounds are shown to be active against the bacterium E. coli. Disk diffusion assays were performed to assess the toxicity of different hydraphile derivatives. Liquid culture tests were conducted to quantitate the dependence of bacterical activity on channel length. It is proposed that hydraphiles are toxic to bacteria as a result of channel formation in the membrane. The bactericidal activity is found to depend at least on the presence of a functional central relay and proper channel length. It is speculated that hydraphiles insert into the bilayer and disrupt the cell's osmotic balance, leading to cell death.

The etiological agent of whooping cough, Bordetella pertussis, destroys the ciliated epithelial cells lining the large airways of infected individuals. This cytopathology can be reproduced in respiratory epithelium by tracheal cytotoxin (TCT), a small peptidoglycan-related molecule purified from the culture supernatant of growing B. pertussis organisms. Using fast atom bombardment mass spectrometry, we analyzed the positive- and negative-ion spectra of the purified, biologically active material and assigned a mass of 921 daltons to TCT. Analysis of fragment ions in these spectra as well as the spectra of the methyl ester and acetylated derivatives of TCT unambiguously defined the primary structure of TCT as N-acetylglucosaminyl-1,6-anhydro-N-acetylmuramylalanyl-gamma- glutamyldiaminopimelylalanine. TCT is therefore identical with the ciliostatic anhydropeptidoglycan monomer released by Neisseria gonorrhoeae and with the neurologically active slow-wave sleep-promoting factor FSu. These and other structurally related glycopeptides containing muramic acid thus form a family of molecules with remarkably diverse biological activities.