ATP synthase from bovine mitochondria: sequences of imported precursors of oligomycin sensitivity conferral protein, factor 6, and adenosinetriphosphatase inhibitor protein

Oligomycin sensitivity conferral protein (OSCP), factor 6 (F6), and ATPase inhibitor protein are all components of the ATP synthase complex of bovine mitochondria. They are encoded in nuclear DNA. Complementary DNA clones encoding the precursors of these proteins have been isolated from a bovine library by using mixtures of synthetic oligonucleotides as hybridization probes, and their DNA sequences have been determined. The deduced protein sequences show that the OSCP, F6, and inhibitor proteins have N-terminal presequences of 23, 32, and 25 amino acids, respectively. These presequences are not present in the mature proteins. It is assumed that they serve to direct the proteins into the mitochondrial matrix. The cDNA clones have also been employed as hybridization probes to investigate the genetic complexity of the three proteins in cows and humans. These experiments indicate that the bovine and human inhibitor and bovine F6 proteins are encoded by single genes but suggest the possibility of the presence in both species of more than one gene (or pseudogenes) for the OSCP.     

Number and pattern of association of chromonemata in the chromosomes of Tradescantia

Summary Analysis of reconstructions, prepared from electron micrographs of successive longitudinal serial sections, has led to the conclusion that the somatic telophase chromosome of Tradescantia paludosa contains four cytologically separable chromonemata. The four represent a pair of pairs, that is, two diplospiremes — one with its two chromonemata arranged helically in dextrorse relationship, and the other with its two in sinistrorse relationship — which are associated to form a tetraspireme. During anaphase and telophase the tetraspireme constitutes the chromosome; during prophase and metaphase the tetraspireme represents one of the two chromatids of the chromosome, which is accordingly an octospireme in terms of the number of cytologically identifiable chromonemata. Loose intertwining of the two tetraspiremes during late prophase accounts for the so-called relational coiling.This paper is dedicated to Professor Hans Bauer on his sixtieth birthday anniversary in appreciation of his contributions to the development of modern cytology.The work reported here was supported in part by Research Grants GM-10499 from the National Institutes of Health, U.S. Public Health Service, and GB-290 from the National Science Foundation, and in part by a NATO fellowship awarded to E. Sparvoli by the Italian National Council of Research.     

Genetic study on indole-3-acetic acid production by ectomycorrhizal Hebeloma species: inter- and intraspecific variability in homo- and dikaryotic mycelia

Summary Interspecific variability of indole-3-acetic acid (IAA)-synthesizing activity was examined within 12 wild strains of different Hebeloma species. Interstrain variability was studied within 11 wild strains of Hebeloma cylindrosporum (Romagnési) and intrastrain variability was considered by using 20 homokaryotic and 50 controlled dikaryotic mycelia belonging to the progeny of one laboratory fruiting strain of this species.The range of variation of IAA-synthesizing activity was of the same order of magnitude within the four groups considered. No correlation was detected between, on one hand, the IAA-synthesizing activity of the mycelia and, on the other hand, their taxonomic position, their geographic origin, or their host plant.Within the progeny of one H. cylindrosporum fruiting strain, 15 of the 50 controlled dikaryons presented an activity higher than that of the original dikaryon. The variation among dikaryons could not be strictly related to the variation in parental homokaryons, indicating that genetic control of this activity probably involves a nonadditive component. Significant additive and nonadditive components of the genetic variation were detected, each of them representing about 50% of the total variation. The nonadditive heritable component could not be explained by a model involving only dominance.     

Quality of a stress-sensitive Cucurbita pepo L. pollen

The quality of Cucurbita pepo L. pollen was studied using field pollinations and the fluorochromatic-reaction test. The extreme sensitivity of this pollen to dehydration and ageing is demonstrated. Controlled stress applied to mature pollen leads to the development of seedless fruits. Molecular signals seem to be involved in the induction of this parthenocarpy. These results indicate the existence of distinct sequences involved in the completion of the fertilization program of pollen. With pollen altered by stress, the fertilization process may be stopped at different stages of its completion. We bring evidence that Cucurbita pepo plants have developed special adaptations in order to compensate for the poor viability of their pollen.Abbreviation FCR fluorochromatic reaction     

Viability of Cururbita pepo pollen: biophysical and structural data

During ageing of the short-lived pollen grains of Cucurbita pepo L., water loss was examined in relation to viability using biophysical (¹H-nuclear magnetic resonance, NMR) and cytological methods (fluorochromatic reaction test, freezefracture and scanning electron microscopy). A semi-logarithmic representation of the pollen weight loss demonstrated the complexity of the dehydration process. A the study of proton loss using ¹H-NMR indicated that two major releases water of had taken place, each with different flux rates. Pulse ¹H-NMR experiments showed the occurrene of non-exponential signal decay as a function of time, indicating the existence of different fractions of water in a pollen grain sample. These fractions leave the pollen grain at different times during pollen dehydration, and one of them (that of the so-called vital water) can be related to pollen viability. The quantity of protons giving a signal during pulse ¹H-NMR experiments was very low when the pollen grains were judged to be dead according to the fluorochromatic test. Freeze-fracture replicas of these dead pollen grains (less than 25% water content) showed that the plasma membrane had become detached from the intine surface; this ultrastructural feature might therefore be involved in the loss of pollen viability.Abbreviations A initial amplitude of the NMR signal - A₂ quantity of water charcterized by T_2-2 - A₅ quantity of water characterized by T_2–5 - FCR fluorochromatic reaction - NMR nuclear magnetic resonance - T₂ transverse relaxation time - T_2-2 T₂ measured with 2 ms between each pulse of radiofrequency - T_2–5 T₂ measured with 5 ms between each pulse of radiofrequency     

Increased expression of the gene for the pro alpha 1(IV) chain of basement-membrane procollagen in cultured skin fibroblasts from two variants of osteogenesis imperfecta.

Fibroblasts from two lethal variants of osteogenesis imperfecta were shown to synthesize increased amounts of type IV procollagen. Previous studies established that one of these variants had a non-functional allele for the pro alpha 2 chain of type I procollagen, whereas the other pro alpha 2(I) allele contained a mutation leading to synthesis of shortened pro alpha 2(I) chains. In the two variants, the relative level of mRNA for pro alpha 1(IV) was 31 and 42% of the level of mRNA for pro alpha 1(I) chains. A value of less than 2% was found for a third lethal and four non-lethal variants of osteogenesis imperfecta. Immunofluorescent staining of fibroblasts from the two variants synthesizing increased amounts of type IV procollagen indicated that a homogeneous population of cells synthesized both type IV and type I procollagen. The results suggest that mutations in the type I procollagen genes that result in osteogenesis imperfecta can be associated with increased expression of the genes for type IV procollagen.     

Purification and characterization of proteins with associated tyrosine protein kinase activity from human B lymphocytes

Burkitt lymphoma cells and their counterpart of normal origin contain proteins with associated tyrosine protein, kinase activity. These proteins were isolated by affinity chromatography and Fast Pressure Liquid Chromatography. Proteins with enzyme activity had an app. M. W. of 47 KDa. This protein in extracts of Burkitt lymphoma cells differed by overall charge and phosphorylation from the 47 KDa protein isolated from B lymphocytes of normal origin. Before and after purification the 47 KDa protein of Burkitt lymphoma cells reacted with an antibody directed against the dodecapeptide Arg-Arg-Leu-Ile-Glu-Asp-Asn-Glu-Tyr-Thr-Ala-Arg (conserved region of pp60src), the 47 KDa protein from B cells of normal origin did not; the same protein from both cell lines reacted with anti-pp60src antibody. These results suggest that a tyrosine protein kinase, related to the products of the src family of oncogenes, is modified in Burkitt lymphoma cells.     

Autoregulated changes in stability of polyribosome-bound beta-tubulin mRNAs are specified by the first 13 translated nucleotides.

The expression of tubulin polypeptides in animal cells is controlled by an autoregulatory mechanism whereby increases in the tubulin subunit concentration result in rapid and specific degradation of tubulin mRNAs. We have now determined that the sequences that are necessary and sufficient to specify mouse beta-tubulin mRNAs as substrates for this autoregulated instability reside within the first 13 translated nucleotides (which encode the first four beta-tubulin amino acids Met-Arg-Glu-Ile). This domain has been functionally conserved throughout evolution, inasmuch as sequences isolated from the analogous region of human, chicken, and yeast beta-tubulin mRNAs also confer autoregulation. Further, for an RNA to be a substrate for regulation, not only must it carry the 13-nucleotide coding sequence, but it must also be ribosome bound and its translation must proceed 3' to codon 41.