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PubMed1990

Isolation and characterization of cDNAs from Lycopersicon esculentum and Arabidopsis thaliana encoding the 33 kDa protein of the photosystem II-associated oxygen-evolving complex.

We have identified and isolated cDNA clones of the 33 kDa protein of the oxygen-evolving complex (OEE1) from Lycopersicon esculentum (tomato) and Arabidopsis thaliana and determined their nucleotide sequences. The cDNA clones and antibodies prepared against OEE1 were used as probes to examine the expression of the oee1 gene with respect to regulation by light, organ specificity, and ripening stage of tomato fruit. The steady-state mRNA level is regulated by light, being present in light-grown plants and absent in etiolated seedlings. The oee1 transcripts that accumulate during growth in the light were reduced to non-detectable or low levels by a 3-day dark treatment. The oee1 gene also exhibits differential expression in various organs of the tomato plant. Steady-state mRNA level was highest in immature leaves and absent in roots while the protein was most abundant in mature leaves and absent in roots. During tomato fruit ripening oee1 mRNA decreases to a low level in the pericarp while the protein level decreases below detection. The expression of oee1 appears to be under the control of a complex mechanism regulating both the amount of RNA and its translation.

Amino Acid Sequence↗
PubMed1992

Proton gradient-driven import of the 16 kDa oxygen-evolving complex protein as the full precursor protein by isolated thylakoids.

The biogenesis of the lumenal 16 kDa protein of the photosynthetic oxygen-evolving complex was analysed using an assay for the import of proteins by isolated thylakoids. The precursor protein is imported with high efficiency in the light in both the presence and absence of stromal extract. Import is almost completely blocked in the dark or if the uncoupler nigericin is present in the light. The data indicate that transport across the thylakoid membrane is driven by a proton motive force in which the proton gradient is the dominant component, and that the full precursor protein can be transported across the thylakoid membrane without prior cleavage by the stromal processing peptidase.

Biological Transport, Active↗
PubMed1989

Characterization of cDNA clones encoding the extrinsic 23 kDa polypeptide of the oxygen-evolving complex of photosystem II in pea.

The 23 kDa polypeptide of the oxygen-evolving complex of photosystem II has been extracted from pea photosystem II particles by washing with 1 M NaCl and purified by anion-exchange chromatography. The N-terminal amino acid sequence has been determined and specific antisera have been raised in rabbits and used to screen a pea-leaf cDNA library in lambda gt11. Determination of the nucleotide sequence of two clones provided the nucleotide sequence for the full 23 kDa polypeptide. The deduced amino acid sequence showed it to code for a mature protein of 186 amino acid residues with an N-terminal presequence of 73 amino acid residues showing a high degree of conservation with previously reported 23 kDa sequences from spinach and Chlamydomonas. Southern blots of genomic DNA from pea probed with the labelled cDNA gave rise to only one band suggesting that the protein is encoded by a single gene. Northern blots of RNA extracted from various organs indicated a message of approximately 1.1 kb, in good agreement with the size of the cDNA, in all chlorophyll-containing tissues. Western blots of protein extracted from the same organs indicated that the 23 kDa polypeptide was present in all major organs of the plant except the roots.

Amino Acid Sequence↗
PubMed1991

The full precursor of the 33 kDa oxygen-evolving complex protein of wheat is exported by Escherichia coli and processed to the mature size.

A full-length cDNA encoding the precursor of the lumenal 33 kDa oxygen-evolving complex protein from wheat was inserted into a prokaryotic expression vector. Cell-free transcription-translation of this construct generates a precursor protein of the correct size. However, when expressed in Escherichia coli, the protein is quantitatively exported into the periplasm and processed to the mature size. The results indicate that the thylakoid transfer sequence of this precursor can function as an internal E. coli export signal.

Biological Transport↗
PubMed1994

How long did it take for life to begin and evolve to cyanobacteria?

There is convincing paleontological evidence showing that stromatolite-building phototactic prokaryotes were already in existence 3.5 x 10(9) years ago. Late accretion impacts may have killed off life on our planet as late as 3.8 x 10(9) years ago. This leaves only 300 million years to go from the prebiotic soup to the RNA world and to cyanobacteria. However, 300 million years should be more than sufficient time. All known prebiotic reactions take place in geologically rapid time scales, and very slow prebiotic reactions are not feasible because the intermediate compounds would have been destroyed due to the passage of the entire ocean through deep-sea vents every 10(7) years or in even less time. Therefore, it is likely that self-replicating systems capable of undergoing Darwinian evolution emerged in a period shorter than the destruction rates of its components (<5 million years). The time for evolution from the first DNA/protein organisms to cyanobacteria is usually thought to be very long. However, the similarities of many enzymatic reactions, together with the analysis of the available sequence data, suggest that a significant number of the components involved in basic biological processes are the result of ancient gene duplication events. Assuming that the rate of gene duplication of ancient prokaryotes was comparable to today's present values, the development of a filamentous cyanobacterial-like genome would require approximately 7 x 10(6) years--or perhaps much less. Thus, in spite of the many uncertainties involved in the estimates of time for life to arise and evolve to cyanobacteria, we see no compelling reason to assume that this process, from the beginning of the primitive soup to cyanobacteria, took more than 10 million years.

Biological Evolution↗
PubMed1993

Antisense RNA for components associated with the oxygen-evolving complex and the Rieske iron/sulfur protein of the tobacco thylakoid membrane suppresses accumulation of mRNA, but not of protein.

Homologous cDNA clones of the nuclear-codes 23- and 33-kDa polypeptides of the oxygen-evolving system, as well as the Rieske iron/sulfur protein, were expressed in antisense or sense orientation under the control of the 35S RNA cauliflower mosaic virus promoter in transgenic tobacco (Nicotiana tabacum, L.) in order to modulate stationary concentrations of transcripts for studying relationships between transcript and protein levels. In all instances, in individuals that contained as little as 10% or less of the transcripts of untransformed plants, the corresponding protein levels were not notably altered. This indicated that the mRNA levels for components under study are not rate-limiting for protein accumulation and that severely reduced amounts of these transcripts still allow normal plant development. Overexpression of the 23-kDa polypeptide by the corresponding cDNA integrated in sense orientation resulted in both higher mRNA and protein levels without detectable enhancement of oxygen evolution. At least some of the excess protein was found in the soluble fraction and not associated with the photosystem-II reaction center. An attempt has been made to reconcile the varied responses obtained using these approaches with different expression patterns.

Electron Transport Complex III↗
PubMed1980

The extinction of slowly evolving dynamical systems.

The time evolution of slowly evolving discrete dynamical systems xi + 1 = T(ri, xi), defined on an interval [0, L], where a parameter ri changes slowly with respect to i is considered. For certain transformations T, once ri reaches a critical value the system faces a non-zero probability of extinction because some xj psi [0, L]. Recent ergodic theory results of Ruelle, Pianigiani, and Lasota and Yorke are used to derive a simple expression for the probability of survival of these systems. The extinction process is illustrated with two examples. One is the quadratic map, T (r, x) = rx (1 - x), and the second is a simple model for the growth of a cellular population. The survival statistics for chronic myelogenous leukemia patients are discussed in light of these extinction processes. Two other dynamical processes of biological importance, to which our results are applicable, are mentioned.

Biological Evolution↗
PubMed1985

Cell proliferation-associated expression of a recently evolved isozyme of triosephosphate isomerase.

An electrophoretically unique, thermolabile isozyme of triosephosphate isomerase (TPI; EC 5.3.1.1) accounts for 10-30% of the enzymatic activity in a range of mitotically active human cells and tissues. This type 2 form (subunit) of human TPI appears in two isozymes, an anodally migrating, relative to the constitutive TPI-1/1 homodimer, TPI-2/2 homodimer and the TPI-1/2 heterodimer with an intermediate mobility. Human cell types expressing the induced isozyme, which is the product of the same structural locus as the constitutive isozyme, include mitogen-stimulated lymphocytes, virally transformed B-lymphoblastoid cells, leukemia-derived T-lymphoblastoid cells, HeLa cells, both normal and transformed fibroblasts, and placental tissue. Extracts of nondividing or terminally differentiated human cells/tissues, such as erythrocytes, striated muscle, peripheral lymphocytes, and platelets, contain high levels of the constitutive TPI-1/1 isozyme but little or undetectable levels of the TPI-1/2 or TPI-2/2 isozyme. The cell division-associated TPI-1/2 and -2/2 isozymes are distinct in electrophoretic mobility from the deamidated forms of the constitutive isozyme. Extracts of dividing gorilla fibroblasts display an isozyme pattern identical to that of proliferating human cells, but various proliferating cells derived from the African green monkey, rabbit, and chicken express only the constitutive isozyme. Thus, expression of the cell division-associated isozyme of TPI is restricted to the hominoids, suggesting a recently evolved modification mechanism which is specifically activated in proliferating cells.

Animals↗
PubMed1993

Domains within the mammalian ornithine decarboxylase messenger RNA have evolved independently and episodically.

Ornithine decarboxylase (ODC) is the first enzyme in the polyamine biosynthetic pathway. We have studied the evolutionary history of the mammalian ODC mRNA, focusing on the rate of accumulation of sequence divergence within specific subregions of the molecule. The phylogenetic relationships among the mRNAs from several mammalian species, including two mouse species, rat, hamster, and human, were determined based upon the numbers of synonymous substitutions in pairwise comparisons of mRNA coding regions. The separation times for the mRNAs were very similar to those for the corresponding species, suggesting that ODC is encoded by orthologous genes in the different species. Analysis of divergence patterns in four subregions, or domains, of the mRNA (the 5'-untranslated region, the coding region, and two domains of the 3'-untranslated region) showed that the domains have evolved in a noncoordinate fashion. Furthermore, evolution of each subregion has been episodic, with periods of both rapid and slow sequence divergence. We suggest that the episodic pattern of ODC mRNA evolution may indicate the existence of selection pressures that were exerted in a time- and domain-specific manner during mammalian speciation.

Amino Acid Sequence↗
PubMed1981

Light and electron microscopic study of ear cartilage in a case of relapsing polychondritis evolving under corticoid treatment.

Light and electron microscope studies of the ear cartilage in a patient with relapsing polychondritis (RP) under corticoid treatment are reported. Unilateral auricular deformation evolved without inflammatory epidoses and the lesions consisted mainly of marginal erosions filled with fine collagen fibrils and containing degenerating perichondrial cells in their basal parts. Degenerative cells were scattered throughout the perichondrium, but cartilage erosions only occurred when numerous cells were affected in a same area. Cartilage outside the eroded zones did not seem to be modified. Cartilage lesions thus appear to be a result of a chondrocyte renewal defect leading to loss of proteoglycans and elastic fibers, with only collagen remaining. These data suggest that inflammation is probably not the initial pathogenic process responsible for cartilage injury in RP, but that a metabolic defect in perichondrial cells might be involved.

Adrenal Cortex Hormones↗
PubMed1992

Untreated neuroborreliosis: Bannwarth's syndrome evolving into acute schizophrenia-like psychosis. A case report.

In general, meningopolyradiculitis (Bannwarth's syndrome, stage 2 of neuroborreliosis) follows a predictable monophasic self-limiting course. In contrast, we report the case of a patient with an untreated meningopolyradiculitis which evolved into acute schizophrenia-like psychosis due to persistent infection with Borrelia burgdorferi. The psychosis resolved within 1 week of treatment with ceftriaxone. This case shows that the usually benign monophasic meningopolyradiculitis may progress to severe CNS complications, which may have implications on current pathophysiological beliefs.

Acute Disease↗
PubMed1981

Mechanisms by which eucaryotic genes evolve.

This paper reviews our current efforts to understand the evolutionary origin of the ovomucoid gene. Sequence analyses have suggested that introns were present in the primordial ovomucoid gene before birds and mammals diverged, about three hundred million years ago. Our work suggests that the present ovomucoid gene has evolved from a primordial ovomucoid gene by two separate intragenic duplications followed by the addition of a final segment which codes for a secretory signal sequence. The three domains of the secreted peptide and also the signal sequence, are constructed by an apparent assembly of exons which code for individual peptide segments. The exact position of introns within the ovomucoid gene has been defined and the results support the theory that introns separate gene segments that code for functional domains of proteins and provide insight into the manner by which eucaryotic genes were constructed during the process of evolution.

Amino Acid Sequence↗
PubMed1989

Ultrasound diagnosis of evolving pyloric stenosis.

Two infants with recurrent episodes of vomiting had upper gastrointestinal barium studies that did not show radiographic features of pyloric stenosis. However, follow-up abdominal sonograms done 1-2 weeks later documented hypertrophic pyloric stenosis, which led to surgery. This entity is not congenital, but an evolving acquired lesion. Therefore, ultrasound is an excellent modality to evaluate and monitor patients clinically suspected of developing hypertrophic pyloric stenosis despite their initially negative imaging studies.

Humans↗
PubMed1994

Abalone myoglobins evolved from indoleamine dioxygenase: the cDNA-derived amino acid sequence of myoglobin from Nordotis madaka.

The cDNA for the unusual 41 kD myoglobin of the abalone Nordotis madaka was amplified by polymerase chain reaction (PCR), and the cDNA-derived amino acid sequence of 378 residues was determined. As with the myoglobin of the related abalone Sulculus diversicolor (Suzuki and Takagi, J. Mol. Biol. 228, 698-700, 1992), the sequence of Nordotis myoglobin showed no significant homology with any other globins, but showed high homology (35% identity) with vertebrate indoleamine 2,3-dioxygenase, a tryptophan degrading enzyme containing heme. The amino acid sequence homology between Nordotis and Sulculus myoglobins was 87%. These results support our previous idea that the abalone myoglobins evolved from a gene for indoleamine dioxygenase, but not from a globin gene, and therefore all of the hemoglobins ard myoglobins are not homologous. Thus, abalone myoglobins appear to be a typical case of convergent evolution.

Amino Acid Sequence↗
PubMed1983

Many gene-regulatory proteins appear to have a similar alpha-helical fold that binds DNA and evolved from a common precursor.

Amino acid and DNA sequence comparisons suggest that many sequence-specific DNA-binding proteins have in common an homologous region of about 22 amino acids. This region corresponds to two consecutive alpha-helices that occur in both Cro and cI repressor proteins of bacteriophage lambda and in catabolite gene activator protein of Escherichia coli and are presumed to interact with DNA. The results obtained here suggest that this alpha-helical DNA-binding fold occurs in many proteins that regulate gene expression. It also appears that this DNA-binding unit evolved from a common evolutionary precursor.

Amino Acid Sequence↗
PubMed1992

Achalasia evolving from segmental aperistalsis.

A 17-year-old woman was evaluated for dysphagia. Radiologic study revealed a rigid segment 10 cm long in the midesophagus, which was found to be aperistaltic on manometric evaluation. The rest of the esophagus and the lower esophageal sphincter were manometrically normal. Four years later the patient was seen for evaluation of severe dysphagia and symptoms of esophageal overflow. Characteristic radiologic and manometric findings of classic achalasia were noted. The case is discussed as an atypical form of achalasia evolving from a segmental esophageal aperistalsis.

Adolescent↗
PubMed2003

Evolving entities and changing concepts in breast pathology.

Among the evolving entities and changing concepts in breast pathology are those relating to columnar cell hyperplasia, pseudoangiomatous stromal hyperplasia, mucocele-like lesions, pleomorphic lobular carcinoma in situ, pseudo-Paget's disease of nipple, microinvasive carcinoma of breast, spindle cell metaplastic carcinoma, and minimal metastatic disease in axillary lymph nodes. Pathologists, as well as physicians involved in the management of breast diseases, need to be aware of these recent developments in breast pathology since the recognition and understanding thereof may have considerable clinical relevance.

Breast Neoplasms↗
PubMed2004

Pathological approach to evolving prognostic and predictive factors of breast cancer.

Among the evolving concepts of prognostic and predictive factors in breast carcinoma pathology are those relating to lymph node status, tumor size, histological type, histological grade, bone marrow micrometastasis, and lymphatic and blood vessel involvement. Correct identification based on a uniform and complete pathological evaluation of tumor specimens is vital to correctly decide treatment. In addition we describe inflammatory cell infiltrates in breast carcinoma as not only prognostic and predictive factors but also pleiotropic regulators and/or effectors.

Breast Neoplasms↗