Decrease of polypeptides in the PS I antenna complex with increasing growth irradiance in the red alga Porphyridium cruentum

Thylakoids isolated from cells of the red alga Porphyridium cruentum exhibit an increased PS I activity on a chlorophyll basis with increasing growth irradiance, even though the stoichiometry of Photosystems I and II in such cells shows little change (Cunningham et al. (1989) Plant Physiol 91: 1179–1187). PS I activity was 26% greater in thylakoids of cells acclimated at 280 mol photons · m^–2 · s^–1 (VHL) than in cells acclimated at 10 mol photons · m^–2 · s^–1 (LL), indicating a change in the light absorbance capacity of PS I. Upon isolating PS I holocomplexes from VHL cells it was found that they contained 132±9 Chl/P700 while those obtained from LL cells had 165±4 Chl/P700. Examination of the polypeptide composition of PS I holocomplexes on SDS-PAGE showed a notable decrease of three polypeptides (19.5, 21.0 and 22 kDa) in VHL-complexes relative to LL-complexes. These polypeptides belong to a novel LHC I complex, recently discovered in red algae (Wolfe et al. (1994a) Nature 367: 566–568), that lacks Chl b and includes at least six different polypeptides. We suggest that the decrease in PS I Chl antenna size observed with increasing irradiance is attributable to changes occurring in the LHC I-antenna complex. Evidence for a Chl-binding antenna complex associated with PS II core complexes is lacking at this point. LHC II-type polypeptides were not observed in functionally active PS II preparations (Wolfe et al. (1994b) Biochimica Biophysica Acta 1188: 357–366), nor did we detect polypeptides that showed immunocross-reactivity with LHC II specific antisera (made to Chlamydomonas and Euglena LHC II).Abbreviations Bis-Tris bis(2-hydroxyethyl)imino-tris(hydroxymethyl)methane - DCPIP 2,6-dichlorophenol indophenol - -dm dodecyl--d-maltoside - HL high light of 150 mol photons · m^–2 · s^–1 - LGB lower green band - LHC I light-harvesting complex of PS I - LHC II light-harvesting complex of PS II - LL low light of 10 mol photons · m^–2 · s^–1 - ML medium light of 50 mol photons · m^–2 · s^–1 - MES 2-(N-morpholino) ethanesulfonic acid - P700 reaction center of PS I - PFD photon flux density - Trizma tris(hydroxymethyl)aminomethane - UGB upper green band - VHL very high light of 280 mol photons · m^–2 · s^–1     

Zfy1 encodes a nuclear sequence-specific DNA binding protein

Zfy1 is a mouse Y chromosomal gene encoding a zincfinger protein which is thought to have some function during spermatogenesis. Here we show that, when introduced into tissue culture cells, Zfy1 is targeted to the nucleus. Two independent signals are present within the protein for nuclear localization. This nuclear Zfy1 protein is able to bind strongly to DNA-cellulose and, using site-selection assays, we have identified specific Zfy1 DNA binding sites. Taken together these results suggest that Zfy1 is a nuclear-located sequence-specific DNA binding protein which functions during spermatogenesis.     

IAP insertion in the murine LamB3 gene results in junctional epidermolysis bullosa

The laminin-5 molecule functions in the attachment of various epithelia to basement membranes. Mutations in the laminin-5-coding genes have been associated with Herlitz junctional epidermolysis bullosa (HJEB), a severe and often lethal blistering disease of humans. Here we report the characterization of a spontaneous mouse mutant with an autosomal recessive blistering disease. These mice exhibit sub-epithelial blisters of the skin and mucosal surfaces and abnormal hemidesmosomes lacking sub-basal dense plates. By linkage analysis the genetic defect was localized to a 2-cM region on distal Chromosome (Chr) 1 where a laminin-5 subunit gene, LamB3, was previously localized. LamB3 mRNA and laminin-5 protein were undetectable by Northern blot analysis and immunohistochemical methods, respectively. DNA sequence analysis indicated that the LamB3 genetic defect resulted from disruption of the coding sequence by insertion of an intracisternal-A particle (IAP) at an exon/intron junction. These findings suggest a role for laminin-5 in hemidesmosome formation and indicate that the LamB3 ^IAP mutant is a useful mouse model for HJEB. Received: 27 March 1997 / Accepted: 14 May 1997     

Alterations in growth and body composition during puberty. I.Comparing multicompartment body composition models

Roemmich, James N., Pamela A. Clark, Arthur Weltman, andAlan D. Rogol. Alterations in growth and body composition duringpuberty. I. Comparing multicompartment body composition models.J. Appl. Physiol. 83(3): 927-935, 1997.A four-compartment (4C) model of body composition was used as acriterion to determine the accuracy of three-compartment (3C) andtwo-compartment (2C) models to estimate percent body fat (%BF) inprepubertal and pubertal boys (genital I & II,n = 17; genital III & IV,n = 7) and girls (breast I & II, n = 8; breast III & IV,n = 15). The 3C water-density (3C-H₂O) and 3C mineral-densitymodels, dual-energy X-ray absorptiometry, the Lohman age-adjustedequations, the Slaughter et al. skinfold equations, and the Houtkooperet al. and Boileau bioelectrical impedance equations wereevaluated. Agreement with the 4C model increased with thenumber of compartments (i.e., body water, bone mineral) measured.Except for the 3C-H₂O model, thelimits of agreement were large and did not perform well forindividuals. The mean %BF by dual-energy X-ray absorptiometry (23.6%)was greater than that of the criterion 4C method (21.7%).For the field methods, the Slaughter et al. skinfold equationsperformed better than did the Houtkooper et al. and Boileaubioimpedance equations. The hydration of the fat-free mass decreased(genital I & II = 75.7%, genital III & IV = 74.8%, breast I & II = 75.5%, breast III & IV = 74.4%) and the mineral content increased(genital I & II = 4.9%, genital III & IV = 5.0%, breast I & II = 5.1%, breast III & IV = 5.7%) with maturation. The densityof the fat-free mass also increased (genital I & II = 1.084 g/ml,genital III & IV = 1.087 g/ml, breast I & II = 1.086 g/ml, breast III & IV = 1.091 g/ml) with maturation. All of the models reduced the %BF overprediction of the Siri 2C model, but only the 4C and3C-H₂O models should be used ascriterion methods for body composition validation in children andadolescents.

     

Ventilation and metabolism among rat strains

Strohl, Kingman P., Agnes J. Thomas, Pamela St. Jean, EvelynH. Schlenker, Richard J. Koletsky, and Nicholas J. Schork. Ventilation and metabolism among rat strains. J. Appl. Physiol. 82(1): 317-323, 1997.We examinedventilation and metabolism in four rat strains with variation in traitsfor body weight and/or blood pressure regulation.Sprague-Dawley [SD; 8 males (M), 8 females (F)], BrownNorway (BN; 10 M, 11 F), and Zucker (Z; 11 M, 12 F) rats were comparedwith Koletsky (K; 11 M, 11 F) rats. With the use of noninvasiveplethysmography, frequency, tidal volume, minute ventilation(E),O₂ consumption, andCO₂ production were derived atrest during normoxia (room air) and during the 5th minute of exposureto each of the following: hyperoxia (100% O₂), hypoxia (10%O₂-balanceN₂), and hypercapnia (7%CO₂-balance O₂). Statistical methods probedfor strain and sex effects, with covariant analysis by body weight,length, and body mass. During resting breathing, strain effects werefound with respect to both frequency (BN, Z > K, SD) and tidal volume(SD > BN, Z) but not to E. Sexinfluenced frequency (F > M) alone. Z rats had higher values forO₂ consumption,CO₂ production, and respiratoryquotient than the other three strains, with no independent effect bysex. During hyperoxia, frequency was greater in BN and Z than in SD orK rats; SD rats had a larger tidal volume than BN or Z rats; Z rats hada greater E than K rats; and M had alarger tidal volume than F. Strain differences persisted duringhypercapnia, with Z rats exhibiting the highest frequency andE values. During hypoxic exposure,strain effects were found to influenceE (SD > K, Z), frequency (BN > K), and tidal volume (SD > BN, K, Z). Body mass was only amodest predictor of E during normoxia, of both E and tidal volume withhypoxia, hypercapnia, or hyperoxia, and of frequency duringhypercapnia. We conclude that strain of rats, more than their body massor sex, has major and different influences on metabolism, the patternand level of ventilation during air breathing, and ventilation duringacute exposure to hypercapnia or hypoxia.

     

GENETIC VARIATION IN TRAGOPOGON SPECIES: ADDITIONAL ORIGINS OF THE ALLOTETRAPLOIDS T. MIRUS AND T. MISCELLUS (COMPOSITAE)

Genetic diversity in the introduced diploids Tragopogon dubius, T. porrifolius, and T. pratensis and their neoallotetraploid derivatives T. mirus and T. miscellus was estimated to assess the numbers of recurrent, independent origins of the two tetraploid species in the Palouse region of eastern Washington and adjacent Idaho. These tetraploid species arose in this region, probably within the past 50–60 yr, and provide one of the best models for the study of polyploidy in plants. The parental species of both T. mirus and T. miscellus have been well documented, and each tetraploid species has apparently formed multiple times. However, a recent survey of the distributions of these allotetraploids revealed that both tetraploid species have expanded their ranges considerably during the past 50 yr, and several new populations of each species were discovered. Therefore, to evaluate the possibility that these recently discovered populations are of recent independent origin, a broad analysis of genetic diversity in T. mirus, T. miscellus, and their diploid progenitors was conducted. Analyses of allozymic and DNA restriction site variation in all known populations of T. mirus and T. miscellus in the Palouse and several populations of each parental diploid species revealed several distinct genotypes in each tetraploid species. Four isozymic multilocus genotypes were observed in T. mirus, and seven were detected in T. miscellus. Tragopogon mirus possesses a single chloroplast genome, that of T. porrifolius, and two distinct repeat types of the 18S-26S ribosomal RNA genes. Populations of T. miscellus from Pullman, Washington, have the chloroplast genome of T. dubius; all other populations of T. miscellus have the chloroplast DNA of T. pratensis. All populations of T. miscellus combine the ribosomal RNA repeat types of T. dubius and T. pratensis, as demonstrated previously. When all current and previously published data are considered, both T. mirus and T. miscellus appear to have formed numerous times even within the small geographic confines of the Palouse, with estimates of five to nine and two to 21 independent origins, respectively. Such recurrent polyploidization appears to characterize most polyploid plant species investigated to date (although this number is small) and may contribute to the genetic diversity and ultimate success of polyploid species.     

Mapping of the α4 subunit gene (GABRA4) to human chromosome 4 defines an α2—α4—β1—γ1 gene cluster: further evidence that modern GABAA receptor gene clusters are derived from an ancestral cluster

We demonstrated previously that an α₁—β₂—γ₂ gene cluster of the γ-aminobutyric acid (GABA_A) receptor is located on human chromosome 5q34–q35 and that an ancestral α—β—γ gene cluster probably spawned clusters on chromosomes 4, 5, and 15. Here, we report that the α₄ gene (GABRA4) maps to human chromosome 4p14–q12, defining a cluster comprising the α₂, α₄, β₁, and γ₁ genes. The existence of an α₂—α₄—β₁—γ₁ cluster on chromosome 4 and an α₁—α₆—β₂—γ₂ cluster on chromosome 5 provides further evidence that the number of ancestral GABA_A receptor subunit genes has been expanded by duplication within an ancestral gene cluster. Moreover, if duplication of the α gene occurred before duplication of the ancestral gene cluster, then a heretofore undiscovered subtype of α subunit should be located on human chromosome 15q11–q13 within an α₅—α_x—β₃—γ₃ gene cluster at the locus for Angelman and Prader—Willi syndromes.     

Bacterial leader peptidase,a membrane protein without a leader peptide,uses the same export pathway as pre-secretory proteins

Leader peptidase typifies a group of proteins of the plasma membrane of E. coli which span the membrane and are synthesized without a cleaved amino-terminal leader (signal) sequence. The membrane assembly properties of these proteins have not been previously reported. We find that the membrane electrochemical potential is necessary for the insertion of a large domain of leader peptidase across the membrane. In the absence of potential, the peptidase accumulates inside the cell in tight association with the. plasma membrane. Upon restoration of the potential, accumulated peptidase inserts across the membrane, indicating that this insertion is not mechanistically coupled to polypeptide chain growth. The normal, trans-bilayer peptidase and that which accumulates in the absence of potential have different conformations, as shown by the relative resistance of the trans-bilayer enzyme to digestion by trypsin or chymotrypsin in cell lysates. Membrane insertion is accompanied by this conformational change. This assembly reaction has several features predicted by the hypothesis of membrane-triggered folding.     

Production of penicillins and cephalosporins in an immobilized enzyme reactor

Summary Four enzymes required for the biosynthesis of pencillins and cephalosporins by Streptomyces clavuligerus have been immobilized on an anion exchange resin. The capabilities of the system have been studied by circulation of reaction mixtures through the immobilized enzyme reactor. Within 30 min, all of the substrate -(l--aminoadipyl)-l-cysteinyl-d-valine is consumed and converted to a mixture of penicillins and cephalosporins. After 60 min the major antibiotic products are (iso)penicillin N and desacetylcephalosporin C. The activity of the immobilized enzyme reactor activity is stable to storage at temperatures below 4°C but activity is lost on repeated use.     

N2O Evolution by Green Algae

Evidence is presented here that axenic cultures of Chlorella, Scenedesmus, Coelastrum, and Chlorococcum spp. evolve N₂O when grown on NO₂⁻, showing that the Chlorophyceae are a source of N₂O in aquatic systems.