Ganglioside and rabbit erythrocyte membrane receptor for staphylococcal alpha-toxin

The hemolytic activity of staphylococcal alpha-toxin is inhibited by an N-acetylglucosamine-containing ganglioside (GlcNAc-ganglioside) but not by any of the related glycolipids. The GlcNAc-ganglioside also is precipitated with the toxin by a gel-diffusion technique. It is postulated that GlcNAc-ganglioside may be the membrane receptor for the alpha-toxin.

Inhibitory effect of flavin mononucleotide on the hemolysis of rabbit erythrocytes by staphylococcal alpha-toxin

Flavin mononucleotide diminished the hemolytic action of staphylococcal alpha-toxin on rabbit erythrocytes by competitive inhibition, probably by its interaction with the alpha-toxin binding sites on the cell membrane.

Assignment of the histidine proton magnetic resonance peaks of soybean trypsin inhibitor (Kunitz) by a differertial deuterium exchange technique

Deuterium exchange at the C(2)-H position of the two histidine residues of native soybean trypsin inhibitor (Kunitz) in 2-H2O was followed by 1-H nuclear magnetic resonance (NMR) spectroscopy. The two histidine residues of soybean trypsin inhibitor exchange at significantly different rates at pH* 5.00, 40 degrees. Half-times observed were: peak H1, t1/2=61 plus or minus 2 days; peak H2, T1/2=24 plus or minus 2 days. Differentially deuterated soybean trypsin inhibitor was cleaved by cyanogen bromide into two fragments each containing one histidine residue. The deuterium content of the histidine residue of each separated fragment was analyzed by 1H NMR spectroscopy. Hisidine-71 in fragment 1-114 showed approximately twice the deuterium content of His-157 in fragment 115-181. These results lead to the assignment of 1H NMR peak H1 to His-157 and peak H2 to His-71. These assignments were extended to the histidine peaks of trypsin-modified soybean trypsin inhibitor by converting the differentially deuterated virgin soybean trypsin inhibitor to the modified form. The correlation of histidine peaks in virgin amd modified soybean trypsin inhibitors was the same as proposed earlier on the basis of pK arguments. The results demonstrate that His-71 is the residue whose pK value is raised from 5.27 to 5.91 on trypsin modification of soybean trypsin inhibitor [Markley, J. L., (1973), Biochemistry 12, 2245].

Neurotological studies upon intoxication by organic mercury compounds

In 1965, a strange illness, which afterwards was diagnosed as the intoxication caused by organic mercury compounds, began to affect the inhabitants of the riverside areas of the Aganogawa River, Niigata, Japan. The authors have investigated the neurotological disturbances, which occurred in 144 cases intoxicated with organic mercurials. The results obtained are summarized as follows: (1) Recruitment (in SISI and other tests) was negative in all the cases except for 32 with inner ear deafness, and Békèsy's AUDIOMETRY (TTS) showed type II: unsettled wide amplitude in 17 cases and severe abnormal adaptation characterizing the type III pattern in nine cases. (2) Spontaneous and positional nystagmus were recorded with ENG in 94 of 144 cases. In 62 of 144 cases, pathological findings of horizontal optokinetic nystagmus were recorded, and those of vertical optokinetic nystagmus were frequently observed in 81 of the 118 cases tested (69 percent). Judging from the authors' observations, neurotological disturbances due to chronic mercurial intoxication may be considered mainly as lesions of the retrocochlea and of the oculomotor system in the brain stem and the cerebellum.

Inhibitory effect of diphtheria toxin on amino acid incorporation in Escherichia coli cell-free system

The mechanism of action of diphtheria toxin in an Escherichia coli cell-free protein-synthesizing system was examined. When the washed ribosomes were incubated with toxin before addition of messenger ribonucleic acid (RNA), peptide syntheses of (14)C-phenylalanine directed by polyuridylic acid or phage R17 RNA were strongly inhibited by a small amount of toxin. Whereas, if the soluble fraction (105,000 x g supernatant fraction) was preincubated with toxin, no effect of toxin occurred either on the induced protein synthesis or on the activity of guanosine triphosphatase even in the presence of nicotinamide adenine dinucleotide. The binding of (3)H-formylmethionyl-transfer RNA to E. coli ribosomes directed by either R17 RNA or trinucleotide AUG was also decreased by toxin. These findings suggest that diphtheria toxin may prevent the binding of messenger RNA by successfully competing with the AUG for ribosomal binding sites. Sucrose-density gradient studies support this concept by showing the decrease in binding of (3)H-labeled R17 RNA to E. coli ribosomes exposed to toxin.