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Full-Text Articles in Biochemistry, Biophysics, and Structural Biology

Protein Turnover As A Component In The Light/Dark Regulation Of PhosphoEnolPyruvate Carboxylase Protein-Serine Kinase Activity In C4 Plants, Jin-An Jiao, Cristina Echevarría, Jean Vidal, Raymond Chollet Jan 1991

Protein Turnover As A Component In The Light/Dark Regulation Of PhosphoEnolPyruvate Carboxylase Protein-Serine Kinase Activity In C4 Plants, Jin-An Jiao, Cristina Echevarría, Jean Vidal, Raymond Chollet

Department of Biochemistry: Faculty Publications

Maize leaf phosphoenolpyruvate carboxylase [PEPC; orthophosphate:oxaloacetate carboxy-lyase (phosphorylating), EC 4.1.1.311 protein-serine kinase (PEPC-PK) phosphorylates serine-15 of its target enzyme, thus leading to an increase in catalytic activity and a concomitant decrease in malate sensitivity of this cytoplasmic C4 photosynthesis enzyme in the light. We have recently demonstrated that the PEPC-PK activity in maize leaves is slowly, but strikingly, increased in the light and decreased in darkness. In this report, we provide evidence that cycloheximide, an inhibitor of cytoplasmic protein synthesis, when fed to detached leaves of C4 monocots (maize, sorghum) and dicots (Portulaca oleracea) in the …


In Vivo Regulatory Phosphorylation Site In C4-Leaf Phosphoenolpyruvate Carboxylase From Maize And Sorghum, Jin-An Jiao, Jean Vidal, Cristina Echevarría, Raymond Chollet Jan 1991

In Vivo Regulatory Phosphorylation Site In C4-Leaf Phosphoenolpyruvate Carboxylase From Maize And Sorghum, Jin-An Jiao, Jean Vidal, Cristina Echevarría, Raymond Chollet

Department of Biochemistry: Faculty Publications

Reversible seryl-phosphorylation contributes to the light/dark regulation of C4-leaf phosphoenolpyruvate carboxylase (PEPC) activity in vivo. The specific regulatory residue that, upon in vitro phosphorylation by a maize-leaf protein-serine kinase(s), leads to an increase in catalytic activity and a decrease in malatesensitivity of the target enzyme has been recently identified as Ser-15 in 32P-phosphorylated/activated dark-form maize PEPC (J-A Jiao, R Chollet [1990] Arch Biochem Biophys 283: 300-305). In order to ascertain whether this N-terminal seryl residue is, indeed, the in vivo regulatory phosphorylation site, [32P]phosphopeptides were isolated and purified from in vivo 32P-labeled maize and …


Purification And Characterization Of Soybean Root Nodule Ferric Leghemoglobin Reductase, Lin Ji, Stephen Wood, Manuel Becana, Robert V. Klucas Jan 1991

Purification And Characterization Of Soybean Root Nodule Ferric Leghemoglobin Reductase, Lin Ji, Stephen Wood, Manuel Becana, Robert V. Klucas

Department of Biochemistry: Faculty Publications

A ferric leghemoglobin reductase from the cytosol of soybean (Glyclne max) root nodules was purified to homogeneity and partlafly characterized. The enzyme is a flavoprotein with flavin adenine dinuclotide as the prosthetic group and consists of two identical subunits, each having a molecular mass of 54 kilodaltons. The pure enzyme shows a high activity for ferric leghemoglobin reduction with NADH as the reductant in the absence of any exogenous mediators. The enzyme also exhibits NADH-dependent 2,6-dichloroindophenol reductase activity. A sequence of the first 50 N-terminal amino acids of the purified protein was obtained. Comparisons with known protein sequences …


Posttranslational Regulation Of Phosphoenolpyruvate Carboxylase In C4 And Crassulacean Acid Metabolism Plants, Jin-An Jiao, Raymond Chollet Jan 1991

Posttranslational Regulation Of Phosphoenolpyruvate Carboxylase In C4 And Crassulacean Acid Metabolism Plants, Jin-An Jiao, Raymond Chollet

Department of Biochemistry: Faculty Publications

Control of C4 photosynthesis and Crassulacean acid metabolism (CAM) is, in part, mediated by the diel regulation of phosphoenolpyruvate carboxylase (PEPC) activity. The nature of this regulation of PEPC in the leaf cell cytoplasm of C4 and CAM plants is both metabolite-related and posttranslational. Specifically, the regulatory properties of the enzyme vary in accord with the physiological activity of C4 photosynthesis and CAM: PEPC is less sensitive to feedback inhibition by L-malate under light (C4 plants) or at night (CAM plants) than in darkness (C4) or during the day (CAM). While the view that …


Nicotinate, Nicotinamide, And The Reactivity Of Leghemoglobin In Soybean Root Nodules, Robert V. Klucas, Cyril A. Appleby Jan 1991

Nicotinate, Nicotinamide, And The Reactivity Of Leghemoglobin In Soybean Root Nodules, Robert V. Klucas, Cyril A. Appleby

Department of Biochemistry: Faculty Publications

Nicotinate has been postulated to interfere with the binding of O2 to ferrous leghemoglobin in soybean (Glycine max) root nodules. For such a function, the levels of nicotinate in nodules must be sufficiently high to bind a significant amount of leghemoglobin. We have measured levels of nicotinate, nicotinamide, and leghemoglobin in soybean nodules from plants 34 to 73 days after planting in a glasshouse. On a per gram nodule fresh weight basis, levels between 10.4 and 21 nanomoles for nicotinate, 19.2 and 37.8 nanomoles for nicotinamide, and 170 to 280 nanomoles for leghemoglobin were measured. Even if …


Detection Of Mercuric Ions In Water By Elisa With A Mercury- Specific Antibody, Dwane E. Wylie, Larry D. Carlson, Randy Carlson, Fred W. Wagner, Sheldon M. Schuster Jan 1991

Detection Of Mercuric Ions In Water By Elisa With A Mercury- Specific Antibody, Dwane E. Wylie, Larry D. Carlson, Randy Carlson, Fred W. Wagner, Sheldon M. Schuster

Department of Biochemistry: Faculty Publications

An immunoassay that detects mercuric ions in water at concentrations of 0.5 ppb and above is described. The assay utilizes a monoclonal antibody that binds specifically to mercuric ions immobilized in wells of microtiter plates. Within the range of 0.5-10 ppb mercury, the absorbance in the enzyme-linked immunosorbent assay (ELISA) is linear to the log of the mercuric ion concentration. The quantitation of mercury by ELISA correlates closely with results from cold-vapor atomic absorption. Other divalent metal cations do not interfere with the assay, although there is interference in the presence of 1 mM chloride ions. The optimum pH for …


Photosynthetic Electron Transport In Genetically Altered Photosystem Ii Reaction Centers Of Chloroplasts, Robin A. Roffey, John H. Golebeck, C. Russ Hille, Richard T. Sayre Jan 1991

Photosynthetic Electron Transport In Genetically Altered Photosystem Ii Reaction Centers Of Chloroplasts, Robin A. Roffey, John H. Golebeck, C. Russ Hille, Richard T. Sayre

Department of Biochemistry: Faculty Publications

Using a cotransformation system to identify chloroplast transformants in Chlamydomonas reinhardtii, we converted histidine-195 of the photosystem H reaction center D1 protein to a tyrosine residue. The mutants were characterized by a reduced quantum efficiency for photosynthetic oxygen evolution, which varied in a pH-dependent manner, a reduced capacity to oxidize artificial donors to photosystem II, and P680+) reduction kinetics (microsecond) that were essentially similar to wild type. In addition, a dark-stable radical was detected by ESR in mutant photosystem II particles but not in wild-type particles. This radical was similar in g value and lineshape to chlorophyll …