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M Edelman

Publications and source records attributed to M Edelman.

At least 19 recordsLinked to original sources
PubMed1999

D1-D2 protein degradation in the chloroplast. Complex light saturation kinetics.

The D1 and D2 proteins of the photosystem II (PSII) reaction center are stable in the dark, while rapid degradation occurs in the light. Thus far, a quantitative correlation between degradation and photon fluences has not been determined. In Spirodela oligorrhiza, D1-D2 degradation increases with photon flux. We find that kinetics for D2 degradation mirror those for D1, except that the actual half-life times of the D2 protein are about three times larger than those of the D1. The degradation ratio, D2/D1, is fluence independent, supporting the proposal [Jansen, M.A.K., Greenberg, B.M., Edelman, M., Mattoo, A.K. & Gaba, V. (1996), Photochem. Photobiol. 63, 814-817] that degradation of the two proteins is coupled. It is commonly conceived that D1 degradation is predominantly associated with photon fluences that are supersaturating for photosynthesis. We now show that a fluence as low as 5 mumol.m-2.s-1 elicited a reaction constituting > 25% of the total degradation response, while > 90% of the degradation potential was attained at intensities below saturation for photosynthesis (approximately 750 mumol.m-2.s-1). Thus, in intact plants, D1 degradation is overwhelmingly associated with fluences limiting for photosynthesis. D1 degradation increases with photon flux in a complex, multiphasic manner. Four phases were uncovered over the fluence range from 0-1600 mumol.m-2.s-1. The multiphasic saturation kinetics underscore that the D1 and D2 degradation response is complex, and emanates from more than one parameter. The physiological processes associated with each phase remain to be determined.

Chloroplasts↗
PubMed1998

Biophysical, biochemical, and physiological characterization of Chlamydomonas reinhardtii mutants with amino acid substitutions at the Ala251 residue in the D1 protein that result in varying levels of photosynthetic competence.

The QB binding site of the D1 reaction center protein, located within a stromal loop between transmembrane helices IV and V formed by residues Ile219 to Leu272, is essential for photosynthetic electron transport through photosystem II (PSII). We have examined the function of the highly conserved Ala251 D1 residue in this domain in chloroplast transformants of Chlamydomonas reinhardtii and found that Arg, Asp, Gln, Glu, and His substitutions are nonphotosynthetic, whereas Cys, Ser, Pro, Gly, Ile, Val, and Leu substitutions show various alterations in D1 turnover, photosynthesis, and photoautotrophic growth. The latter mutations reduce the rate of QA to QB electron transfer, but this is not necessarily rate-limiting for photoautotrophic growth. The Cys mutant divides and evolves O2 at wild type rates, although it has slightly higher rates of D1 synthesis and turnover and reduced electron transfer between QA and QB. O2 evolution, D1 synthesis, and accumulation in the Ser, Pro, and Gly mutants in high light is reduced, but photoautotrophic growth rate is not affected. In contrast, the Ile, Val, and Leu mutants are impaired in photoautotrophic growth and photosynthesis in both low and high light and have elevated rates of D1 synthesis and degradation, but D1 accumulation is normal. While rates of synthesis/degradation of the D1 protein are not necessarily correlated with alterations in specific parameters of PSII function in these mutants, bulkiness of the substituted amino acids is highly correlated with the dissociation constant for QB in the seven mutants examined. These observations imply that the Ala251 residue plays a key role in D1 protein.

Alanine↗
PubMed1997

Evidence for light-dependent and light-independent protein dephosphorylation in chloroplasts.

A number of photosystem II (PSII) associated proteins, including core proteins D1, D2 and CP43, and several proteins of the LHCII complex, are phosphorylated by a thylakoid-bound, redox-regulated kinase(s). We demonstrate here that the compound propyl gallate is an effective inhibitor of LHCII phosphorylation in vivo while having little effect on PSII core protein phosphorylation. Using this inhibitor, we demonstrate that LHCII dephosphorylation is insensitive to light in vivo. Taken together with our previous conclusion (Elich et al., EMBO J. 12 (1993) 4857-4862) that PSII core protein dephosphorylation is light-stimulated, our data suggest the presence of multiple phosphatases responsible for thylakoid protein dephosphorylation in vivo.

Cells, Cultured↗
PubMed1997

Catalytic properties and sensitivity to tentoxin of Chlamydomonas reinhardtii ATP synthases changed in codon 83 of atpB by site-directed mutagenesis.

The participation of the amino acid beta83 in determining the sensitivity of chloroplast ATP synthases to tentoxin was reported previously. We have changed codon 83 of the Chlamydomonas reinhardtii atpB gene by site-directed mutagenesis to further examine the role of this amino acid in the response of the ATP synthase to tentoxin and in the mechanism of ATP synthesis and hydrolysis. Amino acid beta83 was changed from Glu to Asp (betaE83D) and to Lys (betaE83K), and the highly conserved tetrapeptide betaT82-E83-G84-L85 (DeltaTEGL) was deleted. Mutant strains were produced by particle gun transformation of atpB deletion mutants cw15DeltaatpB and FUD50 with the mutated atpB genes. The transformants containing the betaE83D and betaE83K mutant genes grew well photoautotrophically. The DeltaTEGL transformant did not grow photoautotrophically, and no CF1 subunits were detected by immunostaining of Western blots using CF1 specific antibodies. The rates of ATP synthesis at clamped DeltapH with thylakoids isolated from cw15 and the two mutants, betaE83D and betaE83K, were similar. However, only the phosphorylation activity of the mutant betaE83D was inhibited by tentoxin with 50% inhibition attained at 4 microM. These results confirm that amino acid beta83 is critical in determining the response of ATP synthase to tentoxin. The rates of the latent Mg-ATPase activity of the CF1s isolated from cw15, betaE83D, and betaE83K were similar and could be enhanced by heat, alcohols, and octylglucoside. As in the case of the membrane-bound enzyme, only CF1 from the betaE83D mutant was sensitive to tentoxin. A lower alcohol concentration was required for optimal stimulation of the ATPase of the betaE83K-CF1 than that of CF1 from the other two strains. Moreover, the optimal activity of the betaE83K-CF1 was also lower. These results suggest that introduction of an amino acid with a positively charged side chain in position 83 in the "crown" domain affects the active conformation of the CF1-ATPase.

ATP Synthetase Complexes↗
PubMed1997

CASP2 molecular docking predictions with the LIGIN software.

Seven docking predictions were made with the LIGIN program. In six cases the location of the binding pocket was identified correctly by systematically docking everywhere within the protein structure. In two cases the ligand was docked to within 1.8 A RMSD of the experimentally determined structure. LIGIN has not been optimized to deal with highly flexible ligands that dock at the surface of proteins. Consequently, in three cases the exposed part of the ligand was docked poorly, although the buried parts were docked well, and made similar atomic contacts with the protein as in the experimentally determined structure.

Amiloride↗
PubMed1997

Joubert syndrome associated with multicystic kidney disease and hepatic fibrosis.

There are several diseases characterized by renal cysts and neurological abnormalities. Joubert syndrome is distinguished by hypoplasia of the cerebellar vermis, hypotonia, retinal dystrophy characterized by abnormal eye movements, and impaired psychomotor development, together with abnormal respiratory pattern. We describe a boy with Joubert syndrome associated with multicystic renal dysplasia and hepatic fibrosis. We speculate that the association of malformations of the renal and nervous systems in this syndrome and others are not random. Concomitant malformations of these systems are likely based upon their common developmental and genetic features.

Brain↗
PubMed1997

Splenic micro-anatomical localization of small lymphocytic lymphoma/chronic lymphocytic leukemia using a novel combined silver nitrate and immunoperoxidase technique.

Small lymphocytic lymphoma/chronic lymphocytic leukemia (SLL/CLL) may be histologically difficult to differentiate from reactive lymphoid hyperplasia (RLH) in the spleen. Because routine hematoxylin and eosin (H&E) staining delineates splenic microanatomy poorly, we have developed a method that simultaneously stains reticulin fibers and B-lymphocytes. B3 or formalin-fixed, paraffin-embedded archival splenic tissue with diagnoses of SLL/CLL (11 cases), RLH (10 cases), and trauma (seven cases) were studied using a novel silver nitrate immunoperoxidase (SNIP) double-staining technique. Gordon and Sweet's reticulin stain was followed by immunoperoxidase staining for B-lineage marker CD20 (Dakopatts, Carpinteria, CA) using the avidin-biotin method. This allowed us to clearly localize B cells to Malpighian bodies, periarteriolar lymphoid sheaths, sinuses, or cords. Features identified by SNIP found only in SLL/CLL, but not in RLH or traumatized spleens, were trabecular infiltration (eight of 11 cases), subendothelial infiltration (seven of 11 cases), and prominent sinus involvement (seven of 11 cases). One or more of these features were seen in 10 of 11 cases of SLL/CLL. Other distinguishing features were the percentage area occupied by B-lymphocytes in each section (SLL/CLL = 74%; RLH = 46%; traumatized spleens = 36%); and mean spleen weight (SLL/CLL = 1,603 g; RLH = 287 g; traumatized spleens = 126 g). We have found the SNIP technique to be superior to traditional H&E staining in identifying B cells in the context of splenic microanatomy.

Adolescent↗
PubMed1996

Reduced connexin 43 expression in high grade, human prostatic adenocarcinoma cells.

Gap junction-mediated communication is required for normal cellular growth and differentiation. As cancer is thought to be a manifestation of the breakdown of cell-cell communication, with the concomitant loss of growth control, it would be expected that alterations in the primary structure, processing, oligomerization or trafficking of connexin (cxn) molecules would have a profound effect on the neoplastic process. Here we a present a preliminary immunohistochemical and molecular analysis of cxn 43 expression in prostatic epithelial cells from resected human tissue. Our data indicate that benign prostatic epithelial cells express cxn 43 protein, but that this expression is diminished in more advanced, anaplastic cancer cells. These data suggest that decreased connexin expression is not involved in the initiation of prostate cancer, but rather occurs during the progression of the disease.

Adenocarcinoma↗
PubMed1996

The double edged sword of the immune response: mutational analysis of a murine anti-pneumococcal, anti-DNA antibody.

Anti-double-stranded (ds) DNA antibodies are not only an important diagnostic marker for SLE, but also play an important role in tissue injury. Microbial antigen may be a stimulus for the production of these antibodies. We isolated 99D.7E, an IgG2b monoclonal antibody from a nonautoimmune BALB/c mouse that is cross-reactive with both dsDNA and phosphorylcholine, the dominant hapten on the pneumococcal cell wall. While partially protective against a bacterial challenge, 99D.7E is also pathogenic to the kidney. To identify those molecular motifs that confer on anti-PC antibodies the potential for autoreactivity, we created a panel of 99D.7E mutants with single amino acid substitutions in the heavy chain, and examined the changes in antigen binding and renal deposition. Our results support the hypothesis that charge and affinity for dsDNA are not adequate predictors of the pathogenicity of anti-DNA antibodies. Differential renal damage from anti-dsDNA antibodies may be due to differences in fine specificity, rather than differential affinity for dsDNA. Importantly, high affinity IgG antibodies cross-reactive with bacterial and self antigen exist and can display pathogenic potential, suggesting that defects in peripheral regulation of B cells, activated by foreign antigen but cross-reactive with self antigen, might lead to autoimmune disorders.

Amino Acid Sequence↗
PubMed1996

Molecular docking using surface complementarity.

A method is described to dock a ligand into a binding site in a protein on the basis of the complementarity of the intermolecular atomic contacts. Docking is performed by maximization of a complementarity function that is dependent on atomic contact surface area and the chemical properties of the contacting atoms. The generality and simplicity of the complementarity function ensure that a wide range of chemical structures can be handled. The ligand and the protein are treated as rigid bodies, but displacement of a small number of residues lining the ligand binding site can be taken into account. The method can assist in the design of improved ligands by indicating what changes in complementarity may occur as a result of the substitution of an atom in the ligand. The capabilities of the method are demonstrated by application to 14 protein-ligand complexes of known crystal structure.

Algorithms↗
PubMed1996

Pyomyoma after uterine instrumentation. A case report.

BACKGROUND: Since 1945, only 10 cases of pyomyoma have been described in the literature. Four were related to pregnancy but none to elective abortion or uterine instrumentation. CASE: A 32-year-old woman was admitted to the hospital with a history of lower abdominal pain, nausea, vomiting and low grade fever with a past medical history significant for uterine leiomyomata and a second-trimester elective abortion 10 weeks prior to admission. Pelvic sonography demonstrated an enlarged uterus with a mass consisting of cystic and solid components. Uterine curettage revealed blood clots and scanty endometrial tissue. After no improvement following antibiotic therapy and nondiagnostic uterine curettage, an exploratory laparotomy was performed. It revealed peritonitis with multiple pyomyomas draining purulent material. CONCLUSION: Although rarely reported, pyomyoma should be considered in the setting of a recent history of uterine instrumentation, signs of infection and a uterine myoma.

Abortion, Induced↗
PubMed1995

Validation of the determination of amino acids in plasma by high-performance liquid chromatography using automated pre-column derivatization with o-phthaldialdehyde.

A sensitive and reproducible fully automated method for the determination of amino acids in plasma based on reversed-phase high-performance liquid chromatography and o-phthaldialdehyde pre-column derivatization is described. A 5-microns Spherisorb ODS 2 column (125 x 3 mm I.D.) was selected for routine determination. Over 40 physiological amino acids could be determined within 49 min (injection to injection) and 48 samples could be processed unattended. The coefficients of variation for most amino acids in plasma were below 4%. We were also able to measure trace amounts of amino acids in plasma normally not detected in a routine analysis. The results obtained with the method described compared favourably with those of conventional amino acid analysis (r = 0.997) and were in excellent agreement with those of other laboratories (r = 0.999).

Adult↗
PubMed1995

Isolation and spectroscopic characterization of a plantlike photosystem II reaction center from the cyanobacterium Synechocystis sp. 6803.

A chlorophyll-protein complex has been isolated from the cyanobacterium Synechocystis sp. PCC 6803 that closely resembles higher plant photosystem II reaction centers in spectral properties. The Synechocystis complex has a pigment content of 5-7 chlorophyll a molecules:1 Cyt b559:2 pheophytins; an optical absorption redmost transition at approximately 675 nm; and a nonconservative circular dichroism red signal, with extrema at 682 (+) and 652 (-) nm. Upon illumination, the Synechocystis D1/D2/Cyt b559 complex accumulates reduced pheophytin. LDS-PAGE and/or immunoblotting showed the D1, D2, and Cyt b559 proteins, aggregated and degraded forms of D1 and possibly D2, and traces of ATP synthase and the CP47 photosystem II chlorophyll protein. The availability of such a Synechocystis preparation opens the way for employing site-directed mutagenesis in studying primary reactions of oxygenic photosynthesis.

Chlorophyll↗
PubMed1995

Modeling the quinone-B binding site of the photosystem-II reaction center using notions of complementarity and contact-surface between atoms.

Functional identity and significant similarities in cofactors and sequence exist between the L and M reaction center proteins of the photosynthetic bacteria and the D1 and D2 photosystem-II reaction center proteins of cyanobacteria, algae, and plants. A model of the quinone (QB) binding site of the D1 protein is presented based upon the resolved structure of the QB binding pocket of the L subunit, and introducing novel quantitative notions of complementarity and contact surface between atoms. This model, built without using traditional methods of molecular mechanics and restricted to residues in direct contact with QB, accounts for the experimentally derived functional state of mutants of the D1 protein in the region of QB. It predicts the binding of both the classical and phenol-type PSII herbicides and rationalizes the relative levels of tolerance of mutant phenotypes.

Atrazine↗