PET1402, a nuclear gene required for proteolytic processing of cytochrome oxidase subunit 2 in yeast

The nuclear mutation pet ts1402 prevents proteolytic processing of the precursor of cytochrome oxidase subunit 2 (cox2) in Saccharomyces cerevisiae. The structural gene PET1402 was isolated by genetic complementation of the temperature-sensitive mutation. DNA sequence analysis identified a 1206-bp open reading frame, which is located 215 by upstream of the PET122 gene. The DNA sequence of PET1402 predicts a hydrophobic, integral membrane protein with four transmembrane segments and a typical mitochondrial targeting sequence. Weak sequence similarity was found to two bacterial proteins of unknown function. Haploid cells containing a null allelle of PET1402 are respiratory deficient.     

Radiological evaluation of bone status in the jaw and in the vertebral column in a group of women

Vertebral bone mineral content was determined in a group of 56 women, ages 30–62. These measurements were compared with the status of supporting bone in the jaws (alveolar, molar and bicuspid) and with gingival health. There was a significant decline in vertebral bone mineral content from the pre- to post-menopausal group. Molar and bicuspid measurements were highly correlated. There was some association between lumbar bone mineral content and molar bone status for postmenopausal women. For postmenopausal women, the cases of greatest percent bone loss in alveolar crest were associated with lower lumbar bone mineral content. Gingival health did not confound the bone status measurements. The 56 subjects did not exhibit the degree of reduction in bone density that is observed in the general population. Further investigation using these radiographic techniques may reveal a link between substantial bone loss in the jaw and moderate to severe bone loss in the lumbar vertebrae.     

Small angle neutron scattering studies of C8 and C9 and their interactions in solution.

Small angle neutron scattering (SANS) results revealed that contrary to most reports C9 is not a globular protein. Its radius of gyration (Rg) at pH 8 and an ionic strength of 0.5 is 32.2 +/- 1.4 A increasing to 35 A at physiologic ionic strength. In contrast, C8, which has a 2.2-fold larger mass, has a similar Rg value [34.6 +/- 1.6 A]. Calibration plots of Rg vs. M(r) indicate that native C8 is a spherical protein whereas native C9 is elongated. From previous reports it was known that native C8 and C9 associate in solutions of low ionic strength. SANS results confirmed this observation but also demonstrated that C8-C9 heterodimers are already formed at physiologic ionic strength. The dimeric complex is globular [Rg = 40 +/- 0.8 A] indicating that the proteins associate side-by-side rather than end-to-end. In contrast, in presence of the drug Suramin, a potent inhibitor of the assembly of the C5b-9 complex, C9 forms a complex with twice the molecular mass that is still elongated (Rg = 48.8 +/- 0.8 A), suggesting that in this case the protein dimerizes end-to-end via a bridging Suramin molecule.     

Effects of cytosolic calcium and limited, possible dual, effects of G protein modulators on guard cell inward potassium channels

The cellular mechanisms that regulate potassium (K⁺) channels in guard cells have been the subject of recent research, as K⁺ channel modulation has been suggested to contribute to stomatal movements. Patch clamp studies have been pursued on guard cell protoplasts of Vicia faba to analyze the effects of physiological cytosolic free Ca²⁺ concentrations, Ca²⁺ buffers and GTP-binding protein modulators on inward-rectifying K⁺ channels. Ca²⁺ inhibition of inward-rectifying K⁺ currents depended strongly on the concentration and effectiveness of the Ca²⁺ buffer used, indicating a large Ca²⁺ buffering capacity and pH increases in guard calls. When the cytosolic Ca²⁺ concentration was buffered to micromolar levels using BAPTA, inward-rectifying K⁺ channels were strongly inhibited. However, when EGTA was used as the Ca²⁺ buffer, much less inhibition was observed, even when pipette solutions contained 1 µM free Ca²⁺. Under the imposed conditions, GTPγS did not significantly inhibit inward-rectifying K⁺ channel currents when cytosolic Ca²⁺ was buffered to low levels or when using EGTA as the Ca²⁺ buffer. Furthermore, GDPβS reduced inward K⁺ currents at low cytosolic Ca²⁺, indicating a novel mode of inward K⁺ channel regulation by G-protein modulators, which is opposite in effect to that from previous reports. On the other hand, when Ca²⁺ was effectively elevated in the cytosol to 1 µM using BAPTA, GTPγS produced an additional inhibition of the inward-rectifying K⁺ channel currents in a population of cells, indicating possible Ca²⁺-dependent action of GTP-binding protein modulators in K⁺ channel inhibition. Assays of stomatal opening show that 90% inhibition of inward K⁺ currents does not prohibit, but slows, stomatal opening and reduces stomatal apertures by only 34% after 2 h light exposure. These data suggest that limited K⁺ channel down-regulation alone may not be rate-limiting, and it is proposed that the concerted action of proton-pump inhibition and additional anion channel activation is likely required for inhibition of stomatal opening. Furthermore, G-protein modulators regulate inward K⁺ channels in a more complex and limited, possibly Ca²⁺-dependent, manner than previously proposed.     

Temperature-dependent morphological changes in membranes of bacillus stearothermophilus

Bacillus stearothermophilus cells vary the lipid fatty acid composition of cytoplasmic membranes with growth temperature. Spin label studies of such membranes have been interpreted to indicate lateral lipid phase separations at the growth temperature. We have now used freeze-fracture electron microscopy to confirm the spin label studies. Freeze-fracture faces of protoplasts indicate slight but distinct protein aggregation at the growth temperature. Aggregation increases rapidly with decreasing quench temperature in wild-type cells. In contrast we were unable to demonstrate extended protein segregation in membranes of a temperature-sensitive mutant that contains more than 58% branched fatty acids. Storage of protoplasts for prolonged times below the lipid phase transition results in the appearance of corrugated fracture faces with 300- to 500-Å repeat patterns, although this organism does not synthesize lecithins.     

The phenoloxidases of the ascomycete Podospora anserina. XIII. Action and interaction of genes controlling the formation of laccase.

1. Eight mutants were isolated following mutagen treatment which are deficient in laccase formation. Seven of these had a pleiotropic effect and exhibited defects in growth rate and in mycelial and sexual morphology. 2. By means of tetrad analysis the mutations were assigned to 6 loci. Three mutations were in the incolora locus, the others were non-allelic. Only two of these loci were closely linked. 3. All genes exhibit numerous interactions. These concern the morphological expression of the laccase genes and also the laccase spectra. 4. The mutants could be separated into four classes on the basis of the amount and type of laccase produced. 5. Five of the loci studied appear to be structural genes because mutations alters the physical properties of the laccase protein. The sixth gene has a regulatory role.     

Evidence for plasmid like DNA in a filamentous fungus, the ascomycete Podospora anserina

Summary The existece of plasmid like DNA was demonstrated in senescent mycelia of Podospora anserina (strain s) by biophysical and electronmicroscopic methods. According to their contour length of about 1.4 and 2.7 m respectively the molecular weight for the monomer is in the range of 3·10⁶.This work was supported by the Deutsche Forschungsgemeinschaft. The sojourn of P.A.L. for six months in Bochum was made possible by a Senior U.S. Scientist Award of the Alexander von Humboldt Stiftung (Bonn).     

Antiserum to a novel peptide sequence reacts selectively with epithelial subpopulations

A synthetic peptide corresponding to a novel protein sequence isolated from bovine kidney was used to immunize rabbits. When applied to Western blots of bovine kidney extracts, antiserum to this peptide recognizes proteins with molecular weights of 23 and 18 KD. Immunohistochemical examination of a variety of bovine and rat tissues with this antiserum revealed a unique distribution of immunoreactivity with the intermediate layers of a variety of stratified epithelia, in addition to renal glomeruli. The pattern of reactivity differed from previously described epithelial markers such as cytokeratins. These results indicate that this antiserum may be useful as a tool for the identification of cells of the intermediate layer of stratified epithelia and, as such, may aid in the study of this differentiating/proliferating tissue compartment.