[Analysis of extracellular proteome of Staphylococcus aureus 6 at the end of exponential growth phase]

AIM

Determine protein specter that Staphylococcus aureus synthesizes and secretes at early growth phase--the exponential phase.

MATERIALS AND METHODS

Proteins secreted by S. aureus strain 6 into cultivation medium at the end of exponential growth phase (4.5 hours) were studied. 11 proteins were identified by liquid chromatography--mass-spectrometry method.

RESULTS

Only in 3 of these proteins the presence of signal peptides was predicted, which indicates their extracellular localization; the rest of the proteins were localized predominantly in bacterial cytoplasm. 5 of 11 proteins function as enzymes of carbohydrate metabolism. Other extracellular proteins that could indicate its contamination with proteins from disrupted bacterial cells were not detected in S. aureus cultural liquid filtrate. It has been suggested that enzymes of carbohydrate metabolism can provide bacterial cells with energy necessary for passage from lag-phase into exponential growth phase. Superoxide dismutase enzyme probably provides the course of oxidation-reduction processes. Synthesis of other proteolytic enzymes and toxins is carried out at later stages of development of bacterial population. Immunization of mice with a mixture of 11 identified proteins showed their protective properties after infection by S. aureus 6 strain.

CONCLUSION

Based on the above-mentioned, the complex of isolated proteins may be perspective in development of a new strategy of prophylaxis and therapy of staphylococcus infections.

Induction of resistance to murine tumor development is associated with alterations in the glycosylation of blood serum proteins

The phenomenon of accelerated metastatic tumor growth following the removal of the primary tumor is a major reason for cancer relapse, caused by underlying mechanisms that are not as yet understood. We hypothesized that a growth-stimulating factor is produced by the tumor-bearing host. This assumption was confirmed by an experiment involving the removal of a primary tumor (ascitic and solid Ehrlich carcinoma cells) from C57B1/6 mice, after which accelerated proliferation was observed in the remaining tumor cells. Peripheral blood leukocytes (PBLCs), spleen leukocytes (SLCs) and peritoneal cells (PCs) were transferred from donor animals with their tumors removed to healthy animals, along with tumor cells. This procedure suppressed tumor growth in 20-40% of the recipient animals when PBLCs, SLCs or PCs were collected 6-8 h after the removal of the tumor. In a second experiment, PBLCs, SLCs or PCs were injected into the mice, and the tumor cells were inoculated 14 days later. Resistance to tumor development occurred within the same time frame (6-8 h) but was more pronounced (60-80%) than in the previous experiment. Ehrlich carcinoma cells affected the binding of FITC-labeled blood serum glycoproteins in a time-dependent manner. Mass spectrometry revealed that the spectrum of glycopeptides in blood serum taken from control mice differed from the spectra of glycopeptides obtained from mice 8-24 h after the removal of Ehrlich carcinoma cells. Comparable effects were also observed with Cloudman S91 melanoma. In conclusion, the inhibition of tumor growth mediated by donor cells (PBLCs, SLCs and PCs) transferred from operated donor animals to recipient animals indicates the existence of a tumor-regulating factor in blood serum. This phenomenon is associated with characteristic alterations in the glycosylation of blood serum proteins.

Naturally occurring disulfide-bound dimers of three-fingered toxins: a paradigm for biological activity diversification

Disulfide-bound dimers of three-fingered toxins have been discovered in the Naja kaouthia cobra venom; that is, the homodimer of alpha-cobratoxin (a long-chain alpha-neurotoxin) and heterodimers formed by alpha-cobratoxin with different cytotoxins. According to circular dichroism measurements, toxins in dimers retain in general their three-fingered folding. The functionally important disulfide 26-30 in polypeptide loop II of alpha-cobratoxin moiety remains intact in both types of dimers. Biological activity studies showed that cytotoxins within dimers completely lose their cytotoxicity. However, the dimers retain most of the alpha-cobratoxin capacity to compete with alpha-bungarotoxin for binding to Torpedo and alpha7 nicotinic acetylcholine receptors (nAChRs) as well as to Lymnea stagnalis acetylcholine-binding protein. Electrophysiological experiments on neuronal nAChRs expressed in Xenopus oocytes have shown that alpha-cobratoxin dimer not only interacts with alpha7 nAChR but, in contrast to alpha-cobratoxin monomer, also blocks alpha3beta2 nAChR. In the latter activity it resembles kappa-bungarotoxin, a dimer with no disulfides between monomers. These results demonstrate that dimerization is essential for the interaction of three-fingered neurotoxins with heteromeric alpha3beta2 nAChRs.

Characteristics of sarcoplasmic reticulum membrane preparations isolated from skeletal muscles of active and hibernating ground squirrel Spermophilus undulatus

The total Ca-ATPase activity in the sarcoplasmic reticulum (SR) membrane fraction isolated from skeletal muscles of winter hibernating ground squirrel Spermophilus undulatus is approximately 2.2-fold lower than in preparations obtained from summer active animals. This is connected in part with approximately 10% decrease of the content of Ca-ATPase protein in SR membranes. However, the enzyme specific activity calculated with correction for its content in SR preparations is still approximately 2-fold lower in hibernating animals. Analysis of the protein composition of SR membranes has shown that in addition to the decrease in Ca-ATPase content in hibernating animals, the amount of SR Ca-release channel (ryanodine receptor) is decreased approximately 2-fold, content of Ca-binding proteins calsequestrin, sarcalumenin, and histidine-rich Ca-binding protein is decreased approximately 3-4-fold, and the amount of proteins with molecular masses 55, 30, and 22 kD is significantly increased. Using the cross-linking agent cupric-phenanthroline, it was shown that in SR membranes of hibernating ground squirrels Ca-ATPase is present in a more aggregated state. The affinity of SR membranes to the hydrophilic fluorescent probe ANS is higher and the degree of excimerization of the hydrophobic probe pyrene is lower (especially for annular lipids) in preparations from hibernating than from summer active animals. The latter indicates an increase in the microviscosity of the lipid environment of Ca-ATPase during hibernation. We suggest that protein aggregation as well as the changes in protein composition and/or in properties of lipid bilayer SR membranes can result in the decrease of enzyme activity during hibernation.

The effects of afferent stimulation on neurons in slices of the medial septal area and their modulation by biologically active substances in hibernating and awake ground squirrels

Evoked neuron activity in slices of the medial septal area and its modulation by neuropeptides and monoamines was studied in two groups of ground squirrels--hibernating and awake animals. Electrical stimulation of the medial forebrain bundle evoked predominantly inhibitory effects of different durations. In addition, responses were seen consisting of resetting of the phase of background volleys to the stimulus after initial inhibition: there were also small numbers of short-latency single-spike responses. All the neuropeptides tested. which had been identified from the brains of hibernating animals, induced differentiated reversible effects consisting of modulation of responses; changes in evoked activity were seen significantly more often than shifts in spontaneous activity. The effects depended on the state of the animal. Thus. peptide TSKYR increased the duration of inhibition in hibernating ground squirrels but shortened inhibition in awake animals. Peptide TSKY. which had little effect in hibernating animals, increased the duration of inhibition in awake animals. Dipeptide DY. which decreased the duration of inhibition and increased the amplitude of the activatory components of responses in hibernating ground squirrels. had little effect in awake animals. The effects of noradrenaline and serotonin correlated to a large extent with their effects on spontaneous activity. It is suggested that endogenous substances are involved in creating the conditions required for increasing the latent excitability and reactivity of septal neurons during hibernation. This allows the medial septal area to function as a "sentry post," allowing the receipt of signals and urgent arousal during hibernation.