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Biomedical subjects

M Edelman

Publications and source records attributed to M Edelman.

At least 55 records · Page 3Linked to original sources
PubMed1991

Direct selection for paternal inheritance of chloroplasts in sexual progeny of Nicotiana.

The response of Nicotiana tabacum to tentoxin (chlorosis) is inherited with chloroplasts. N. tabacum var. Xanthi, a tentoxin-resistant line, was used to pollinate tentoxin-sensitive N. tabacum line 92, an alloplasmic male-sterile line containing N. undulata plastids. The seeds were mutagenized with nitrosomethylurea and germinated in the presence of tentoxin. Two percent of the seedlings had green sectors in their first true leaves. These plants were grown to maturity under non-selective conditions. Homogeneous tentoxin-resistant lines were obtained in the third generation. DNA analysis indicated, however, that selection for paternal plastids, rather than mutagenesis of maternal ones, had occurred in the tentoxin-resistant progeny. Mitochondria, which were not under selection pressure, were inherited maternally as expected. Inheritance of tentoxin-resistant paternal plastids did not require seed mutagenesis. Normally germinated seedlings that were kept under tentoxin selection consistently produced a low level of resistant green sectors in their first true leaves. Thus, normal, low-frequency transmission of paternal plastids in N. tabacum can be directly revealed by using tentoxin.

Chloroplasts↗
PubMed1990

A novel metabolic form of the 32 kDa-D1 protein in the grana-localized reaction center of photosystem II.

Two forms of the 32 kDa-D1 reaction center protein of photosystem II (PSII), having slightly different mobilities on denaturing polyacrylamide gels, have been resolved in Spirodela oligorrhiza, Glycine max L., Gossypium hirsutum L., Triticum aestivum L., and Zea mays L. The protein band with faster mobility is identified as the 32 kDa-D1 protein, and the less mobile band as a novel form, designated 32*. The two forms are structurally similar based on immunological and partial proteolytic tests. 32* is associated exclusively with the grana and is present in the PSII reaction center. Temporally, 32* appears several hours after the translocation of newly synthesized and processed 32 kDa-D1 protein from the stroma lamellae to the grana. Formation of the 32* is strictly light-dependent under physiological light intensities and correlates with a reciprocal loss of the 32-kDa form. Light induced formation of 32* is inhibited by 3-(3,4-dichlorophenyl)-1,1-dimethylurea but is not coupled to linear electron transport.

2,4-Dinitrophenol↗
PubMed1989

A point mutation in the gene for the large subunit of ribulose 1,5-bisphosphate carboxylase/oxygenase affects holoenzyme assembly in Nicotiana tabacum.

In photosynthetic eukaryotes, the enzyme ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) is composed of eight large and eight small subunits. Chloroplast-coded large subunits are found in association with chaperonins (binding proteins) of 60-61 kd to form a high mol. wt pre-assembly complex (B-complex). We have isolated a heterotrophic, maternally-inherited mutant from Nicotiana tabacum var. Xanthi which accumulates the B-complex but contains no Rubisco holoenzyme. The B-complex of the mutant dissociates in the presence of ATP, as does that of the wild-type. Processing of the nuclear-coded small subunit takes place in the mutant and neither large nor small subunits accumulate. The large subunit gene from mutant and wild-type plants was cloned and sequenced. A single nucleotide difference was found between them predicting an amino acid change of serine to phenylalanine at position 112 in the mutant. Based on the resolved structure of N.tabacum Rubisco, it is argued that the alteration at position 112 prevents holoenzyme assembly by interfering with large subunit assembly.

Amino Acid Sequence↗
PubMed1989

Ribosomal protein S12 as a site for streptomycin resistance in Nicotiana chloroplasts.

A streptomycin resistant Nicotiana plastome mutant, X/strR6, was subjected to molecular analysis. In this mutant, a single nucleotide transition, C----T, in the chloroplast gene for ribosomal protein S12 alters codon 90 from proline to serine while the nucleotide sequence of the chloroplast 16 S rRNA gene is identical to that of the wild type. Mutant X/strR6 thus differs from several previously reported streptomycin resistant chloroplast mutants which are altered in the gene for 16 S rRNA.

Base Sequence↗
PubMed1989

Separate photosensitizers mediate degradation of the 32-kDa photosystem II reaction center protein in the visible and UV spectral regions.

A component of the photosystem II reaction center, the 32-kDa protein, is rapidly turned over in the light. The mechanism of its light-dependent metabolism is largely unknown. We quantified the rate of 32-kDa protein degradation over a broad spectral range (UV, visible, and far red). The quantum yield for degradation was highest in the UVB (280-320 nm) region. Spectral evidence demonstrates two distinctly different photosensitizers for 32-kDa protein degradation. The data implicate the bulk photosynthetic pigments (primarily chlorophyll) in the visible and far red regions, and plastoquinone (in one or more of its redox states) in the UV region. A significant portion of 32-kDa protein degradation in sunlight is attributed to UVB irradiance.

Chlorophyll↗
PubMed1988

Injuries of the inferior vena cava.

Beginning in 1946, 577 patients with inferior vena cava injuries were managed at a single institution. After decreasing from 37 to 30 percent, the mortality rate showed a distinct increase in the last 7 years studied. This increase was related to an increasing percentage of patients who arrived in the emergency center in severe shock and required resuscitative thoracotomy. In-hospital care advances have not kept pace with improvements in prehospital care. Although venous complications have not been infrequent, morbidity has not been a significant long-term problem. Fatal pulmonary embolism occurred and was a special problem for patients over the age of 50. More basic research is needed to expedite diagnosis and vascular control in addition to understanding and treating the severe metabolic problems of patients dying from shock and hemorrhage.

Adolescent↗
PubMed1987

Evidence for in vivo trans splicing of pre-mRNAs in tobacco chloroplasts.

The rps12 gene codes for chloroplast ribosomal protein S12. In the tobacco chloroplast genome (156 kbp circular DNA), exons II and III of this gene are separated by an intron of 536 bases and are present in two copies in the inverted repeat region, while exon I is located in the large single copy region at a distance of 90 kb and 126 kb from the two copies of exons II and III. These three exons were artificially combined in cloned DNA fragments and hybridized with tobacco chloroplast RNA. Electron microscopic analysis of RNA-DNA hybrids showed that exon I is transcribed as part of a polycistronic RNA containing upstream and downstream sequences; the same is true for exons II and III. Exon I is shown to be transcribed separately from exons II and III. In the most abundant class of the hybridized RNA molecules, exon I was covalently linked to exon II. In these molecules the sequences downstream of exon I and upstream of exon II are not present. These data indicate that maturation of rps12 pre-mRNAs in chloroplasts of tobacco involves trans splicing.

Chloroplasts↗
PubMed1987

Identification of a primary in vivo degradation product of the rapidly-turning-over 32 kd protein of photosystem II.

The 32 kd photosystem II protein of plant chloroplasts is rapidly turned over in the light. The initial events in the degradation of the 32 kd protein were studied. A 23.5 kd breakdown product was identified in Spirodela oligorrhiza membranes using immunological analysis. The 23.5 kd polypeptide was shown to be derived from the amino-terminal portion of the 32 kd protein using partial proteolytic fingerprinting. An in vivo precursor--product relationship between the 32 kd protein and the 23.5 kd polypeptide was kinetically demonstrated by radiolabeling and pulse-chase experiments. The cleavage site yielding the 23.5 kd polypeptide was localized to a functionally active region (between helices IV and V) of the 32 kd protein. We propose that an alpha-helix-destabilizing 'degradation' sequence, bordered by arginine residues 225 and 238, is involved in the formation of the 23.5 kd polypeptide.

Chlorophyll↗
PubMed1987

Intramembrane translocation and posttranslational palmitoylation of the chloroplast 32-kDa herbicide-binding protein.

The 32-kDa herbicide-binding protein, a component of photosystem II, is synthesized as a membrane-associated 33.5-kDa precursor within the chloroplast. We show that membrane attachment of the precursor and processing to the 32-kDa form occur in the unstacked stromal lamellae. Once processed, the 32-kDa protein translocates, within the thylakoids, to the topologically distinct stacked granal lamellae. Posttranslational palmitoylation of the processed 32-kDa protein is also shown to occur. This modification takes place in a membrane-protected domain and is mainly confined to the protein assembled in the granal lamellae, where functional photosystem II centers are concentrated.

Acylation↗
PubMed1986

The enigma of the gene coding for ribosomal protein S12 in the chloroplasts of Nicotiana.

A 2.9 kbp region from within the inverted repeat of Nicotiana chloroplast DNA hybridized with a chloroplast DNA fragment from Euglena containing the complete rps12 gene coding for ribosomal protein S12. Nucleotide sequencing within this region revealed the existance of two rps12 coding stretches interrupted by 540 bp having class II intron structure. Joining and decoding the exon regions produced a sequence of 85 amino acids colinear and 81% homologous to the S12 protein of Euglena chloroplasts and E. coli, starting from amino acid residue 38 to the stop codon. Immediately upstream of codon 38, conserved intron sequences were located. However, the 5' 37 codon of Nicotiana chloroplast rps12 could not be identified by electron microscopy of RNA-DNA hybrids within a DNA region extending 4000 bp upstream of codon 38, nor by computer search of a completely sequenced region extending for more than 9000 bp upstream of this codon. In E. coli, alteration in rps12 codons 42 or 87 causes streptomycin resistance. However, the nucleotide sequence of the identified rps12 exons in two Nicotiana chloroplast mutants resistant to streptomycin were found to be identical to that of wild type.

Amino Acid Sequence↗
PubMed1984

Chloroplast-coded atrazine resistance in Solanum nigrum: psbA loci from susceptible and resistant biotypes are isogenic except for a single codon change.

The 32-kDa photosystem II protein of the chloroplast is thought to be a target molecule for the herbicide atrazine. The psbA gene coding for this protein was cloned from Solanum nigrum atrazine-susceptible ('S') and atrazine-resistant ('R') biotypes. The 'S' and 'R' genes are identical in nucleotide sequence except for an A to G transition, predicting a Ser to Gly change at codon 264. The same predicted amino acid change in psbA was previously shown for an Amaranthus hybridus 'S' and 'R' biotypes which had, in addition, two silent nucleotide changes between the genes (Hirschberg, J. and McIntosh, L., Science 222, 1346-1349, 1983). Occurrence of the identical, non-silent change in psbA in different 'S' and 'R' weed biotype pairs suggests a functional, herbicide-related role for this codon position.

Amino Acid Sequence↗
PubMed1984

Molecular architecture of the rapidly metabolized 32-kilodalton protein of photosystem II. Indications for COOH-terminal processing of a chloroplast membrane polypeptide.

The molecular architecture of the rapidly metabolized 32-kilodalton chloroplast protein was investigated. Modified proteolytic techniques were applied to construct a cleavage map for this photosynthetic membrane component. The portion which anchors the protein to the membrane was shown to be rich in hydrophobic amino acid residues, while the surface-exposed portion was richer in polar residues. The amino to carboxy polarity of the map was established by comparing oligopeptide radiolabeling data with the polypeptide sequence decoded from the gene. This showed that the anchor domain contains the NH2 terminus, and the exposed domain the COOH terminus. The 32-kilodalton protein was previously demonstrated to derive from a 33.5-kilodalton precursor. We now show that the precursor molecule has a COOH-terminal oligopeptide extension. A model relating precursor cleavage to membrane integration is presented. COOH-terminal processing is proposed to ensure a correct sequence of events for assembly of the 32-kilodalton protein into the photosynthetic membrane.

Amino Acid Sequence↗
PubMed1983

Clone bank of Nicotiana tabacum chloroplast DNA: mapping of the alpha, beta and epsilon subunits of the ATPase coupling factor, the large subunit of ribulosebisphosphate carboxylase, and the 32-kDal membrane protein.

All of the PstI restriction fragments of the chloroplast DNA of Nicotiana tabacum have been cloned in the plasmid vector pBR322. The cloned fragment sizes range from 0.8 to 26 kb, are stable, and can be amplified by chloramphenicol with varying efficiencies. Using these clones we have detailed a PstI physical map of the tobacco chloroplast genome. Selected clones of SalI, BamHI and PstI fragments were used to localize the map positions of the alpha, beta, and epsilon subunits of the chloroplast ATPase coupling factor, the large subunit of ribulosediphosphate carboxylase and the 32-kDal membrane protein. The gene products of these clones were characterized by RNA transcript sizing, immunoprecipitation of maxicell-directed protein synthesis, and hybrid-arrested translation.

Chloroplasts↗
PubMed1982

General occurrence and structural similarity of the rapidly synthesized, 32,000-dalton protein of the chloroplast membrane.

A rapidly metabolized membrane protein from Spirodela, with an apparent molecular weight of 32,000, has been implicated in allosterically regulating electron transport and mediating diuron herbicide sensitivity in the chloroplast (Mattoo, A. K., Pick, U., Hoffman-Falk, H., and Edelman, M. (1981) Proc. Natl. Acad. Sci. U. S. A. 78, 1572-1576). Rapid synthesis of a 32,000-dalton plastid membrane protein is demonstrated for several diverse angiosperms and the alga, Chlamydomonas. Comparative partial proteolytic mapping of the polypeptide showed similar patterns for all species tested. In some cases, a 33,500-dalton precursor polypeptide was identified which also displayed interspecific structural homologies. Lastly, in situ analysis of the surface-exposed 32,000-dalton membrane protein yielded a common trypsinization pattern for the organisms studied. These findings point toward a broad distribution and phylogenetic similarity of the 32,000-dalton thylakoid protein of the chloroplast at levels of precursor maturation, membrane orientation, and primary structure.

Chloroplasts↗
PubMed1982

Cytoplasmic hybridization in Nicotiana: mitochondrial DNA analysis in progenies resulting from fusion between protoplasts having different organelle constitutions.

Our previous studies indicated that fusion products with one functional nucleus but organelles of the two fusion partners (i.e. heteroplastomic cybrids) could be obtained by fusing X-irradiated (cytoplasmic donor) with non-irradiated (recipient) Nicotiana protoplasts. The present report deals with the analysis of mitochondria in cybrid populations resulting from the fusion of donor Nicotiana tabacum protoplasts with recipient protoplasts having a N. Sylvestris nucleus but chloroplasts of an alien Nicotiana species, and exhibiting cytoplasmic male sterility. The two fusion parents showed significant differences in restriction patterns of their chloroplast and mitochondrial DNA. Four groups of cybrid plants were obtained by this fusion. All had N. sylvestris nuclei but contained either donor or recipient chloroplasts and had either sterile or fertile anthers. There was no correlation between anther fertility and chloroplast type. The mitochondrial DNA restriction patterns of sterile cybrids were similar to the respective patterns of the sterile fusion partner while the mitochondrial DNA restriction patterns of the fertile cybrids were similar to the respective patterns of the fertile fusion partner. The results indicate an independent assortment of chloroplasts and mitochondria from the heteroplastomic fusion products.

Cell Fusion↗
PubMed1982

Processing of a chloroplast-translated membrane protein in vivo. Analysis of the rapidly synthesized 32 000-dalton shield protein and its precursor in Spirodela oligorrhiza.

The 32 000-dalton (Da) shield protein regulating electron transport in Spirodela oligorrhiza is an integral chloroplast membrane polypeptide. It is rapidly synthesized, constituting a major chloroplast-translation product in vivo. Following in vitro translation of spirodela chloroplast RNA in a wheat germ system, a 33 500-Da polypeptide is produced. Synthesis of a 33 500-Da protein, associated with the chloroplast membrane, is also seen in vivo, within 2 min of pulse-labeling spirodela with radioactive amino acids. Comparative analyses among these polypeptides reveal: (a) all three are deficient in lysine residues; (b) the two 33 500-Da species have indistinguishable partial proteolytic digestion patterns while that for the 32 000-Da protein differs only slightly from them; (c) radioactivity from the 33 500-Da polypeptide is rapidly chased in vivo into the 32 000-Da protein, even in the presence of protein synthesis inhibitors. These results show the 33 500-Da proteins synthesized in vitro and in vivo to be the precursor form of the 32 000-Da shield protein in spirodela, with processing commencing only after completion of the precursor polypeptide chain and insertion into the membrane.

Cell Membrane↗