Overlapping transcription of the nifA regulatory gene in Rhizobium meliloti

Gene fusions were used to demonstrate complex overlapping transcriptional controls of the regulatory gene nifA in Rhizobium meliloti bacteroids isolated from alfalfa root nodules. Gene nifA has previously been shown to be transcribed from promoter PnifA and to be required for activation of promoters P1 (nifHDK) and P2 (fixABC) during symbiotic nitrogen fixation with alfalfa. P2 is located approximately 4 kb upstream from nifA and is shown in this report to be responsible for at least one-half of the nifA expression observed in bacteroids. Substantial transcription of nifA occurs during symbiosis as evidenced by the fact that PnifA was found to be 53% as active as either P1 or P2. Together, the data indicate that more than half of the transcripts initiated at P2 fail to terminate before reaching nifA. Additional studies indicated that there may be weak promoter activity in the symbiotically essential region downstream from nifA.

Discrepancies in fluorescent antibody, counterimmunoelectrophoresis, and Neufeld test for typing of Streptococcus pneumoniae

The techniques of fluorescent antibody (FA) and counterimmunoelectrophoresis (CIE) were compared with the Neufeld test (quellung reaction) for typing of Streptococcus pneumoniae. A total of 88 isolates were examined by these three methods. Pool-, type-, or group-specific pneumococcal antisera were used in all three methods. Each isolate was initially tested with polyvalent antisera and all of the nine pools of antisera. Selection of the type- or group-specific antisera depended upon the reaction of the isolate with the pool sera. Sixty-eight of 88 (77.3%) isolates were positive using pool or typing sera and were correctly typed by CIE, while FA was found to be accurate for only 61 of 88 (69.3%) isolates. Positive reactions with more than one pool- or type-specific antisera, or no reaction, were seen with several of the isolates with both techniques. Even though CIE and FA are rapid and simple techniques, microbiologists should be cautious when utilizing them for typing of S. pneumoniae because of the discrepancies observed in this study.

Three-dimensional reconstruction of cytochrome oxidase vesicle crystals prepared by cholate solubilization

Cytochrome oxidase vesicle crystals with long-range order have been obtained from cholate-solubilized, highly purified reconstitutively active preparations. These crystals, which are suitable for electron-microscopic structure investigation, show pgg symmetry in the 0 degree projection. Using Fourier reconstruction and modified back-projection methods, a three-dimensional reconstruction has been obtained at a resolution of 25 A. Our structural results are in agreement with the model of Henderson et al. [J. Mol. Biol. 112, 631 (1977)] obtained for their Triton-derived crystals.

Acidic ribosomal proteins of Neurospora crassa

Neurospora crassa acidic ribosomal proteins from the high salt-ethanol extract of 80 S ribosomes have been fractionated by DEAE-cellulose chromatography. Six acidic ribosomal proteins were purified. All resemble Escherichia coli L7 and L12 in amino acid composition and molecular weight but each has a slightly different net charge at pH 3.2. Four have an apparent molecular weight of approx. 14 000, and two have a molecular weight of approx. 14 800. The amino acid compositions and circular dichroism (CD) spectra of the purified Neuropsora proteins are identical for the four 14 kDa proteins, but clearly distinguishable from the two 14.8 kDa proteins. The latter are also identical in amino acid composition and CD spectra. This suggests that there are two Neurospora acidic, or 'A', proteins, one of which exists in four microheterogeneous forms and the other exists in two forms.

Kinetics of electron transfer between cardiac cytochromes c1 and c

Highly purified cytochrome c1, which consists of only one heme peptide and does not form a stable c1-c complex (c1-H-c complex), was used in studies of electron transfer between cytochrome c1 and c. Results show that a stable and ionic-strength-sensitive c1-c complex (i.e., the c1-H-c complex) in the forms of the various oxidation states is not required, in contrast to the current belief of the participation of the complex in the electron transfer between cytochromes c1 and c. A minimum mechanism for electron transfer between these two cytochromes is suggested in accord with the experimental results.

Catalysis of nitrosyl transfer reactions by a dissimilatory nitrite reductase (cytochrome c,d1)

The dissimilatory nitrite reductase (cytochrome c,d1) from Pseudomonas aeruginosa was observed at pH 7.5 to catalyze nitrosyl transfer (nitrosation) between [15N]nitrite and several N-nucleophiles or H2 18O, with rate enhancement of the order of 10(8) relative to analogous chemical reactions. The reducing system (ascorbate, N,N,N',N'-tetramethylphenylenediamine) could reduce nitrite (but not NO) enzymatically and had essentially no direct chemical reactivity toward nitrite or NO. The N-nitrosations showed saturation kinetics with respect to the nucleophile and, while exhibiting Vmax values which varied by about 40-fold, nevertheless showed little or no dependence of Vmax on nucleophile pKa. The N-nitrosations and NO-2/H2O-18O exchange required the reducing system, whereas NO/H2O-18O exchange was inhibited by the reducing system. NO was not detected to serve as a nitrosyl donor to N-nucleophiles. These and other kinetic observations suggest that the enzymatic nitrosyl donor is an enzyme-bound species derived from reduced enzyme and one molecule of nitrite, possibly a heme-nitrosyl compound (E-FeII X NO+) for which there is precedence. Nitrosyl transfer to N-nucleophiles may occur within a ternary complex of enzyme, nitrite, and nucleophile. Catalysis of nitrosyl transfer by nitrite reductase represents a new class of enzymatic reactions and may present another example of electrophilic catalysis by a metal center. The nitrosyl donor trapped by these reactions is believed to represent an intermediate in the reduction of nitrite by cytochrome c,d1.

Bacterial and fungal growth in intravenous fat emulsions

Growth of bacterial and fungal organisms in i.v. fat emulsions was studied. A total of 81 isolates of 15 bacterial and fungal strains were used to inoculate (in test tubes) 10% soybean oil emulsion (Intralipid, Cutter Laboratories), 10% safflower oil emulsion (Liposyn, Abbott Laboratories), trypticase soya broth, and 0.9% sodium chloride at about 2500 organisms/ml. Duplicate samples and negative controls were prepared. Samples were handled under two procedures after inoculation: (1) initially refrigerated overnight, then stored at room temperature for 24 hours, and (2) stored only at room temperature for 24 hours. Samples were taken at 3, 7, and 24 hours after the samples were placed at room temperature, and colony counts were performed. Most organisms grew equally well in the fat emulsions and trypticase soya broth. Fungal strains grew more slowly than bacterial strains but reached equal numbers by 24 hours. Organisms grew quite slowly in sodium chloride, and negative controls showed no growth. These i.v. fat emulsions supported bacterial and fungal growth at the same level as trypticase soya broth.

A mitochondrial protein essential for the formation of the cytochrome c1-c complex. Isolation, purification, and properties

A new mitochondrial protein was isolated to pure form. This protein was indispensable for the formation of the cytochrome c1-c complex; hence, it was provisionally named the hinge protein for formation of the cytochrome c1-c complex, or for simplicity, merely called the hinge protein. The simplest method for the preparation of the pure protein involved essentially pH 5.5 treatment of high purity of "two-band" cytochrome c1 prepared from an improved method. The use of two band cytochrome c1 prepared by an improved method was preferred because the improved method apparently yielded less tight bonding between the heme-containing and colorless protein entities than that from the original methods (King, T. E. (1978) Methods Enzymol. 53, 181-191). The c1-c complex comprised 1 molar equivalent each of the hinge protein, "one-band" cytochrome c1 and cytochrome c. It was demonstrated by gel filtration chromatography that in the absence of the hinge protein, there was no complex formation between cytochromes c and one-band c1. In titration of the complex formed between one-band cytochrome c1 and cytochrome c with the hinge protein present by using the increase of the Soret-Cotton effect as a criterion (Chiang, Y. L., Kaminsky, L. S., and King, T. E. (1976) J. Biol. Chem. 251, 29-36), a sharp break was observed which showed the three species to be present in equivalent amounts. The hinge protein showed low extinction in the 280 nm region and exhibited poor color value and diffuse character of the band in sodium dodecyl sulfate-polyacrylamide gel electrophoresis after staining with Coomassie brilliant blue. The molecular weight was found to be (i) 9,800 from sedimentation equilibrium, (ii) 11,000 from sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and (iii) 23,000 with a Stokes radius of 22.4 A from gel filtration chromatography estimated from a standard curve with proteins of known molecular parameters. The disparities in these data from the actual value of 9,175 from calculations based on amino acid sequence, as previously reported (Wakabayashi, S., Takeda, H., Matsubara, H., Kim, C. H., and King, T. E. (1982) J. Biochem. (Tokyo) 91, 2077-2085), have been discussed.

15N tracer studies on the reduction of nitrite by the purified dissimilatory nitrite reductase of Pseudomonas aeruginosa. Evidence for direct production of N2O without free NO as an intermediate

Nitrite reductase (cytochrome c,d1) was purified from Pseudomonas aeruginosa. In the presence of the reducing system, ascorbate-N,N,N',N'-tetramethylphenyl-enediamine, which alone had no ability to reduce nitrite or NO at pH 7.5, the enzyme catalyzed the reduction of nitrite to NO and N2O as major and minor products, respectively, as determined by gas chromatography-mass spectrometry. The rate of reduction of NO to N2O was considerably lower than the rate of reduction of nitrite to N2O and might be zero. The N2O produced in a system containing [15N]nitrite and natural NO was more highly enriched in 15N than was the NO pool and, in this regard, closely resembled the enrichment of the nitrite pool. The amount of 14N in the NO pool changed little, if any, as the result of enzymatic processes. For the enzyme, free NO seems not to be an intermediate between nitrite and N2O, just as was found by this laboratory for certain intact denitrifying bacteria. The results are consistent with reduction of nitrite to enzyme-bound NO, which can partition between release and further reduction.

Messenger RNA for ribosomal proteins in yeast

The concentrations and mean lifetimes of the messenger RNAs for four ribosomal proteins of the yeast, Saccharomyces cerevisiae, have been determined by the method of approach to equilibrium labeling, using cloned genes as hybridization probes. In cells growing in a minimal medium with glucose as a carbon source, there are roughly equimolar amounts of the four mRNAs, whose half-lives are very similar: 14 +/- 2 minutes, approximately 10% of a generation time. These results lead to an analysis of the economy of mRNA for ribosomal proteins that suggests that the mRNAs may be substantially underutilized.

Mild temperature shock alters the transcription of a discrete class of Saccharomyces cerevisiae genes

In Saccharomyces cerevisiae the synthesis of ribosomal proteins declines temporarily after a culture has been subjected to a mild temperature shock, i.e., a shift from 23 to 36 degrees C, each of which support growth. Using cloned genes for several S. cerevisiae ribosomal proteins, we found that the changes in the synthesis of ribosomal proteins parallel the changes in the concentration of mRNA of each. The disappearance and reappearance of the mRNA is due to a brief but severe inhibition of the transcription of each of the ribosomal protein genes, although the total transcription of mRNA in the cells is relatively unaffected by the temperature shock. The precisely coordinated response of these genes, which are scattered throughout the genome, suggests that either they or the enzyme which transcribes them has unique properties. In certain S. cerevisiae mutants, the synthesis of ribosomal proteins never recovers from a temperature shift. Yet both the decline and the resumption of transcription of these genes during the 30 min after the temperature shift are indistinguishable from those in wild-type cells. The failure of the mutant cells to grow at the restrictive temperature appears to be due to their inability to process the RNA transcribed from genes which have introns (Rosbash et al., Cell 24:679-686, 1981), a large proportion of which appear to be ribosomal protein genes.

Emergence of beta-lactamase-producing strains of Branhamella catarrhalis as important agents of acute otitis media

We performed a prospective study to monitor changes in the bacterial etiology of acute otitis media. Branhamella catarrhalis was isolated from middle ear exudates of 3 of 47 children (6.4%) studied between September 1979 and September 1980 and from 26 of 98 children (26.5%) studied between October 1980 and February 1982 (P = 0.0055). Twenty of 26 B. catarrhalis strains (76.9%) were found to be resistant to ampicillin and to produce beta-lactamase. In contrast only 2 of 26 strains of Haemophilus influenzae (7.7%) isolated from the same group of patients were resistant to ampicillin. We could not detect changes in culture methods, in demographic features, in patterns of medical care or in prior middle ear disease or antimicrobial drug usage, which might explain this striking increase in the relative importance of resistant strains of B. catarrhalis.

Synthesis and pharmacological activity of 6-aryl-2-azabicyclo[4.2.1]nonanes

A series of 6-phenyl-, 6-(m-methoxyphenyl)-, and 6-(m-hydroxyphenyl)-2-azabicyclo[4.2.1]nonanes was synthesized by a sequence involving alkylation of an appropriate 2-arylcyclopentanone with an aminoalkyl substituent. Subsequent ring closure at the other alpha position on the cyclopentanone ring and Wolff-Kishner reduction afforded the title compound. Several derivatives of these materials showed activity in an antinociceptive assay comparable to codeine. Most analogues were either inactive or toxic.

Structural studies of bovine heart cytochrome c1

The complete primary structure of bovine heart cytochrome c1 was established by analyses of peptide fragments prepared by digestion using trypsin, staphylococcal protease, and chymotrypsin and by cyanogen bromide cleavage of cytochrome c1 and its derivatives. The total number of amino acid residues is 241, giving a molecular weight of 27,924 including the heme group. The NH2- and COOH-terminal residues are serine and lysine, respectively. One characteristic of the protein is that cytochrome c1 contains 43.6% hydrophobic residues and the polarity is estimated to be 41.1%. No clear homology was found between cytochrome c1 and other membranous proteins such as cytochrome b5 or the subunits of cytochrome oxidase for which sequences have been reported. Cytochrome c1 is predicted to have a high content of alpha-helix (46%). Partial sequence studies were also carried out on cytochrome c1 preparations obtained by different procedures and showed that there is no difference among the sequences of various preparations of cytochrome c1. The presence of a hydrophobic cluster near the COOH-terminal region indicates that the COOH-terminal region of cytochrome C1 associates with, or is buried in, the phospholipid bilayer of the mitochondrial membrane.

13N isotope studies on the pathway of ammonia assimilation in Bacillus megaterium and Escherichia coli

The pathway of ammonia incorporation into amino acids was studied by use of 13N-ammonium ions in Bacillus megaterium and Escherichia coli that had been grown aerobically on a minimal salts medium containing NH4Cl as the source of nitrogen. Anion- and cation-exchange high-pressure-liquid chromatography was used to separate amino acids relevant to the several possible pathways for ammonia assimilation in bacteria. At an initial concentration of added NH4+ of 1 microM, the glutamine synthetase-glutamate synthase pathway represented the major pathway in both bacteria on the basis of the effects of inhibitors of that pathway (L-methionine-DL-sulfoximine and azaserine) and of transamination (aminooxy-acetate) and the observation that the specific activity of glutamine was greater initially than that of any other amino acid likely to be the first product of an assimilation pathway. The study provides (i) a new analytical method for 13N-tracer investigation of amino acids, (ii) confirmation of conclusions from enzymological studies on the pathway of ammonia assimilation in B. megaterium and E. coli, and (iii) proof that alanine dehydrogenase and aspartate ammonia lyase (aspartase) are not important pathways in B. megaterium at low NH4+ concentrations.

Identity of the heme-not-containing protein in bovine heart cytochrome c1 preparation with the protein mediating c1-c complex formation--a protein with high glutamic acid content

A heme-not-containing protein was isolated from cytochrome c1 preparation by gel filtration after carboxymethylation and citraconylation. The amino acid sequence of this protein was determined by the analysis of tryptic and chymotryptic peptides as well as by solid-phase sequence analysis. It consisted of 78 amino acid residues and the molecular weight was calculated to be 9,175. This protein contained a high proportion of glutamic acid and glutamine (27% of the total residues) but no methionine, isoleucine, tyrosine, and tryptophan. The most notable feature was an acidic cluster of 8 consecutive glutamic acid residues near the amino(N)-terminus). The secondary structure was predicted to have a high proportion of helical content. The amino acid composition and N-terminal sequence of a protein independently prepared from bovine heart mitochondria, which is essential to the formation of the cytochrome c1-c complex, suggested that this colorless factor and the present heme-not-containing protein are identical. Evidence shows that another protein, called the non-heme protein, isolated from "two-band" cytochrome c1 preparation is also the same protein as that presented in this paper.

Traumatic primary intraventricular hemorrhage

Two patients with primary intraventricular hemorrhage following mild head injury are presented. Both patients experienced a rapid loss of consciousness after a lucid interval following the head injury. Conray ventriculography or computerized tomography revealed intraventricular hematoma originating in the third ventricle and causing an obstructive hydrocephalus. Both patients made good recoveries promptly after ventricular drainage.

The genes for fifteen ribosomal proteins of Saccharomyces cerevisiae

We have isolated recombinant lambda phage carrying the genes for 14 of the ribosomal proteins of the yeast Saccharomyces cerevisiae. Analysis of these and of the plasmid carrying the gene tcm1, which codes for the ribosomal protein responsible for resistance to trichodermin, demonstrates that in general the genes for ribosomal proteins are unlinked. One exceptional recombinant carries the genes for two ribosomal proteins within a 2-kilobase region. DNA fragments bearing individual ribosomal protein genes were used to probe restriction digests of the yeast genome to determine whether any of the genes were duplicated. Only 3 of 12 of the genes are present unequivocally as a single copy. Similar fragments were used to probe blots of mRNA separated on denaturing agarose gels to determine the size of the mRNA for each protein. In each case, the mRNA is near the minimum size necessary to code for its protein. In certain temperature-sensitive mutants which fail to synthesize functional mRNA for ribosomal protein, Rosbash et al. (Rosbash, M., Harris, P. K. W., Woolford, J., and Teem, J. L. (1981) Cell, 24, 679-686) have demonstrated the accumulation of a larger RNA molecule, homologous to a ribosomal protein gene, that appears to be a transcript which retains an intervening sequence. We find that for 8 of the 11 ribosomal protein genes examined, a larger molecule accumulates in such a mutant strain, suggesting that in general transcripts of ribosomal protein genes may have introns.

Fenestration of the anterior cerebral artery

Three cases of angiographically demonstrated fenestration of the anterior cerebral artery are reported. Fenestration occurred at the medial half of the horizontal segment of the anterior cerebral artery in all cases. Its embryology and clinical significance are briefly discussed, and the anatomical and radiological literature on fenestration of the anterior cerebral artery is reviewed.