Isoforms of yeast cytochrome c oxidase subunit V affect the binuclear reaction center and alter the kinetics of interaction with the isoforms of yeast cytochrome c

Subunit V, one of the nuclear-coded subunits of yeast cytochrome c oxidase, has two isoforms, Va and Vb. These alter the in vivo intramolecular rates of electron transfer within the holoenzyme (Waterland, R. A., Basu, A., Chance, B., and Poyton, R. O. (1991) J. Biol. Chem. 266, 4180-4186). The isozyme with Vb has a higher turnover rate and a higher intramolecular transfer rate than the isozyme with Va. To determine how these isoforms affect catalysis, we have examined their effects on the binuclear reaction center and on the interaction between cytochrome c oxidase and the two isoforms, iso-1 and iso-2, of yeast cytochrome c. Infrared spectroscopy of carbon monoxide liganded to heme a3 has revealed a single conformer for the binuclear reaction center in the isozyme with Vb but two discrete conformers in the isozyme with Va. The kinetics of interaction for all four pairwise combinations of isozymes with each subunit V isoform and the two cytochrome c isoforms are biphasic, with high and low affinity electron transfer reactions. In general, the isoforms of cytochrome c and subunit V do not alter the Km but do affect the TNmax. The TNmax for isozymes carrying Vb are higher at both high and low affinity sites for each cytochrome c isoform. Iso-1-cytochrome c supports a higher TNmax than Iso-2-cytochrome c. Surprisingly, the combinatorial effect of both sets of isoforms on TNmax is minimized with the pairs of isoforms (iso-1-cytochrome c and subunit Va or iso-2 and subunit Vb) that are co-expressed in cells. Together, these findings support the conclusion that the subunit V isoforms modulate catalysis and suggest that they do so by affecting the environment or structure of the binuclear reaction center. They also suggest that the coexpression of the two cytochrome c isoforms with two subunit V isoforms serves to minimize differences in electron transfer rates brought about by the subunit V isoforms.

The influence of vasectomy and vasovasostomy on testicular ATPases, cAMP, ABP and androgen receptor in rabbits

The present study was performed to further clarify the influences of vasectomy on functions of testis and to disclose the possible mechanisms of infertility after vasovasostomy (VV). Thirty-one rabbits were divided into sham-operated control group (C), vasectomy control group (V), VV fertility group (VaF) and VV infertility group (VaI). Serum testosterone (ST) level, testicular cAMP, androgen binding protein (ABP), nuclear androgen receptor (NAR) concentrations, testis cell membrane Na(+)-, K(+)-ATPase, Mg(2+)-ATPase activities, sperm density and testis weight were measured. Vasectomy resulted in significantly reduced cAMP, Na(+)-, K(+)-ATPase, Mg(2+)-ATPase, testis weight and increased ABP; VV completely restore testis weight in VaF and VaI, Na(+)-, K(+)-ATPase, Mg(2+)-ATPase in VaF, partly cAMP in VaF and VaI, Na(+)-, K(+)-ATPase, Mg(2+)-ATPase in VaI, but did not restore ABP. The NAR content in VaI was significantly lower than those in C, VaF and V. No statistical differences among 4 groups were seen in Kd values for [3H]-T. ST levels in VaF, VaI and V were insignificantly different compared with C, but the value in VaF was higher than that in VaI (p < 0.05). Sperm density after VV reached 122 +/- 62 x 10(6)/ml in VaF and 10 +/- 24 x 10(6)/ml in VaI, both in VaF and VaI were significantly low compared with C (p < 0.001), and the value in VaI was remarkedly lower than that in VaF (p < 0.001). It was shown that sperm density was positively correlated with cAMP content, Na(+)-, K(+)-ATPase, Mg(2+)-ATPase activities, but negatively with ABP. These results suggest that vasectomy gives rise to damage to the testis, and vasovasostomy does not appear completely effective in reversing testicular changes.

Infrared characterization of nitric oxide bonding to bovine heart cytochrome c oxidase and myoglobin

The stable binding of nitric oxide to both Cu+B and Fe2+a3 in cytochrome c oxidase is shown in infrared spectra. The N-O stretch band for Fe2+a3-NO at 1610 cm-1 is similar to the band for MbNO at 1612 cm-1. The Cu+B-NO band is at 1700 cm-1. Thus, electron donation from metal to NO is greater with Fe2+a3 than Cu+B. However, the affinity for NO is only slightly greater at Fe2+a3 than at Cu+B. In contrast CO binds stably only to Fe2+a3. Infrared spectra of oxidase, myoglobin and hemoglobin NO and CO complexes are consistent with only one stable protein structure at the ligand binding site of nitrosyls and with dynamic multiple protein conformers at carbonyl sites. The binding of NO to both Cu+B and Fe2+a3 of cytochrome c oxidase can contribute to NO cytotoxicity and to the catalysis of NO reduction to N2O and makes possible the effective use of infrared spectroscopy in investigations of Cu as well as Fe at the binuclear O2 reduction sites of oxidases.

Characterization of sites occupied by the anesthetic nitrous oxide within proteins by infrared spectroscopy

We report here a comprehensive infrared spectroscopic study of the interactions between the anesthetic nitrous oxide (N2O) and six proteins: lysozyme, cytochrome c, myoglobin, hemoglobin, serum albumin, and cytochrome c oxidase. Sites occupied by N2O molecules within these proteins were characterized. Three types of hydrophobic sites were found within the proteins. One with nu 3 near 2225 cm-1 is likely to be near peptide bond carbonyls; one with nu 3 near 2219 cm-1 may be near a benzene-like structure such as the side chains of phenylalanine and tyrosine; and the other with nu 3 near 2215 cm-1 is likely to be in a nonpolar alkane-like environment provided by the side chains of Leu, Ile, and Val residues. The amount of N2O molecules bound to myoglobin increases as the pH decreases from 9.2 to 5.2. N2O-protein interactions produced no detectable changes in the ligand-binding pockets of myoglobin, hemoglobin, and cytochrome c oxidase. N2O-induced secondary structure changes were detected only in the fully reduced cytochrome c oxidase, not in the fully oxidized oxidase and the other five proteins. N2O-induced conformational changes in the alpha beta-interface of hemoglobin and the h2 and h3 alpha-helices of human serum albumin were detected by monitoring the S-H stretch vibrations of cysteine residues. These findings provide direct evidence that anesthetic N2O interacts with proteins and occupies sites in the interior of the proteins.

Isolation and sequence of the Candida albicans FAS1 gene

The gene (FAS1) encoding the beta-subunit of fatty-acid synthase (FAS) of Candida albicans has been isolated and analyzed. The gene was isolated on the basis of homology to the Saccharomyces cerevisiae FAS1 gene. Sequence analysis showed that the gene contained an intron-free open reading frame of 6111 bp encoding a protein of 2037 amino acids (aa) (227 916 Da). C. albicans FAS1 and its product exhibit a high degree of overall sequence relatedness to their counterparts in S. cerevisiae, with identities of 68 and 63% at the nucleotide (nt) and aa level, respectively. In addition, the beta-subunits of both organisms contain the catalytic domains in an identical sequential order. Northern blots demonstrated that the gene encodes a single mRNA of approx. 6.1 kb, and that changes in transcript levels are not a prerequisite of the yeast-to-hyphal transition. Southern blot analysis of C. albicans chromosomes separated by pulsed-field gel electrophoresis showed that FAS1 resides on chromosome 5.

Characterization of interactions of nitric oxide with human hemoglobin A by infrared spectroscopy

Infrared spectra permit direct measurements of cysteine thiols as well as nitric oxide bound to heme iron in human hemoglobin A nitrosyl. A single symmetric N-O stretch band of nitric oxide bound to Fe2+ is detected amid strong water and protein bands in the Hb14N16O minus Hb15N16O difference spectrum. Nitric oxide accepts electron density from metal in bent-end-on FeI2+)-14N-16O (nu NO = 1616.5 cm-1) and donates electron density to metal in linear Fe(3+)-14N-16O (nu NO = 1925 cm-1). S-H stretch bands reveal that changes in protein conformation occur at alpha-104, beta-93, and beta-112 cysteines upon conversion of deoxyHb to HbNO but that no reactions of thiols with NO occur. Furthermore, no infrared band for S-nitrosothiol is detected. Changes in amide I spectra reflect NO binding induced changes in protein secondary structure.

Probing heart cytochrome c oxidase structure and function by infrared spectroscopy

IR spectra directly probe specific vibrators in bovine heart cytochrome c oxidase, yielding quantitative as well as qualitative information on structures and reactions at these vibrators. C-O IR spectra reveal that CO binds to Fe2+ a3 as two conformers each in isolated immobile environments sensitive to Fea and/or CuA oxidation state but remarkably insensitive to pH, medium, anesthetics, and other factors that affect activity. C-N IR spectra reveal that the one CN- that binds to fully and partially oxidized enzyme can be in three different structures. These structures vary in relative amounts with redox level, thereby reflecting dynamic electron exchange among Fea, CuA, and CuB with associated changes in protein conformation of likely significance in O2 reduction and H(+)-pumping. Azide IR spectra also reflect redox-dependent long-range effects. The amide I IR bands, due to C-O vibrators of peptide linkages and composed of multiple bands derived from different secondary structures, reveal high levels of alpha-helix (approximately 60%) and subtle changes with redox level and exposure to anesthetics. N2O IR spectra reveal that these anesthetic molecules at clinically relevant levels occupy three sites of different polarity within the enzyme as the enzyme is reversibly, but only partially, inhibited.

Purification of beta-lactamases and enzyme kinetic studies on aztreonam

Standard beta-lactamases K1, P99, TEM-1, SHV-1 and beta-lactamase K-CAZ purified using FPLC through ion-exchange chromatography and filtration chromatography, were identified by determination of isoelectric points, molecular weights and substrate profiles. The results showed that the beta-lactamase stability of domestic aztreonam was very similar to that of cefotaxime, ceftazidime and much better than that of cefoperazone. Aztreonam showed a high affinity to chromosomal-mediated cephalosporinase P99, its Ki for inhibition of P99 with cephaloridine as substrate was 0.0159 microns. Aztreonam and the three third generation cephalosporins tested were not stable to beta-lactamase K-CAZ, which hydrolysed them in different degrees.

Nucleotide sequence of the Staphylococcus aureus signal peptidase II (lsp) gene

The lsp gene encoding prolipoprotein signal peptidase (signal peptidase II) of Staphylococcus aureus was cloned by screening a genomic library for plasmid clones capable of complementing a conditionally lethal lsp allele of Escherichia coli. E. coli cells carrying one of five overlapping clones exhibited increased resistance to globomycin. The nucleotide sequence of the S. aureus lsp gene was determined. The deduced amino acid sequence of the signal peptidase II of S. aureus suggests that this enzyme has a hydropathy profile very similar to those of E. coli, Enterobacter aerogenes and Pseudomonas fluorescens. Comparison of the primary structures of this enzyme from these four distinct bacterial species reveals three highly conserved domains in proteins which have a low degree of overall sequence homology. Unlike the lsp genes from the Gram-negative bacteria, the lsp gene in S. aureus is not flanked by x-ileS and orf149-orf316 as found in E. coli, Ent. aerogenes, and P. fluorescens.

Relationship between hormone profiles and the restoration of spermatogenesis in men treated with gossypol

Gossypol acetic acid was administered orally to 35 male volunteers at a dose of 20 mg once a day for 52-70 days in the loading phase and twice a week for 22 months in the maintenance phase. Sperm counts and the serum concentrations of LH, FSH, prolactin, testosterone and oestradiol were monitored regularly during treatment and for a follow-up period of 12 months. At around 90 days after treatment, all treated participants approached or attained azoospermia and remained at this level throughout the maintenance phase. By the end of the follow-up phase, eight treated men were still azoospermic, while sperm counts in the other 27 men were restored to normal levels. The only hormone that changed significantly during and after the treatment was FSH. From the 6th month of the treatment to the end of the follow-up phase, serum concentrations of FSH in the eight participants that reached irreversible azoospermia were significantly higher than in the other 27 men or in controls. It is suggested that monitoring of FSH levels might be of diagnostic use for identifying those participants with irreversible azoospermia during gossypol treatment.

DNA sequence analysis of the recA genes from Proteus vulgaris, Erwinia carotovora, Shigella flexneri and Escherichia coli B/r

The complete nucleotide sequences of the recA genes from Escherichia coli B/r, Shigella flexneri, Erwinia carotovora and Proteus vulgaris were determined. The DNA sequence of the coding region of the E. coli B/r gene contained a single nucleotide change compared with the E. coli K12 gene sequence whereas the S. flexneri gene differed at 7 residues. In both cases, the predicted proteins were identical in primary structure to the E. coli K12 RecA protein. The DNA sequences of the recA genes from E. carotovora and P. vulgaris were 80% and 74% homologous, respectively, to the E. coli K12 gene. The predicted amino acid sequences of the E. carotovora and P. vulgaris RecA proteins were 91% and 85% identical respectively, to that of E. coli K12. The RecA proteins from both P. vulgaris and E. carotovora diverged significantly in sequence in the last 50 residues whereas they showed striking conservation throughout the first 300 amino acids which include an ATP-binding region and a subunit interaction domain. A putative LexA repressor binding site was localized upstream of each of the heterologous genes.

Clinical and experimental studies on paediatric pneumonia treated by lung easing tablets

197 cases of paediatric pneumonia from 2 hospitals were treated by Ning Fei Pian (NFP, the Lung Easing Tablets), a proprietary Chinese medicine for antipyresis, detoxication, blood invigoration, resolution of cough and phlegm; the control group was treated by penicillin, and the therapeutic results were comparable. Examinations of microcirculation and hemorrheology in the nailbed revealed improvements by NFP, which were conducive to the recovery of pneumonia. Electron-microscopically, the tablets also produced improvements in microcirculation, relief of lung edema, and the ratio of ventilation and blood flow.

Al and Ca Alteration of Membrane Permeability of Quercus rubra Root Cortex Cells

This study was undertaken to quantify the effect of aluminum and calcium on membrane permeability. The influence of Ca(2+) (0.2-3.7 millimolar) and Al(3+) (0-3.7 millimolar) on the permeability of root cortical cells of Quercus rubra was measured using three nonelectrolytes (urea, methyl urea, and ethyl urea) as permeators of progressively increasing lipid solubility. Water permeability was also measured. Al(3+) (a) increased membrane permeability to the nonelectrolytes, (b) decreased the membrane's partiality for lipid permeators, and (c) decreased membrane permeability to water. Ca(2+) had effects on permeability that were opposite to those of Al(3+). When Al(3+) and Ca(2+) were tested in combination, these opposite effects counteracted each other. The results suggest that Al(3+) altered the architecture of membrane lipids.