Mediator structure and conformation change

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Rapid in Vivo Acylation of Acyl Carrier Protein with Exogenous Fatty Acids in Spirodela oligorrhiza

Posttranslational acylation of several chloroplast proteins with palmitic acid was recently demonstrated in Spirodela oligorrhiza (AK Mattoo, M Edelman [1987] Proc Natl Acad Sci USA 84: 1497-1501). We have now identified an in vivo acylated, soluble protein having an apparent M_r of 10 kilodaltons on sodium dodecyl sulfate-polyacrylamide gel electrophoresis as an acylated form of acyl carrier protein (ACP). This 10-kilodalton protein is present in low abundance, and its acylation is light-stimulated. Turnover of the acyl moiety but not the apo-protein is rapid in the light. The acylated 10-kilodalton protein coelectrophoreses with in vitro synthesized palmitoyl-acyl carrier protein and is immunoprecipitated from soluble extracts with an antibody raised against spinach ACP. Cerulenin, an inhibitor of β-ketoacyl-ACP synthetase, inhibited in vivo acylation of Spirodela ACP. Cell-free extracts of Spirodela plants were able to catalyze the transfer of palmitate from palmitoyl-CoA to ACP, suggesting the existence in higher plants of a pathway for acylation of ACP that involves transacylation from acyl-CoA.     

Translational modification of an 18 kilodalton polypeptide by spermidine in rice cell suspension cultures

When rice (Oryza sativa) cell suspension cultures are grown in the presence of [terminal methylenes-³H]spermidine, label is incorporated in a single polypeptide with a molecular mass of 18 kilodaltons on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Preincubation of cell cultures with polyamine biosynthesis inhibitors difluoromethylarginine and difluoromethylornithine, resulted in increased incorporation of the label into the 18 kilodalton polypeptide. In cells in which protein synthesis was arrested by cycloheximide, no label was detected in the 18 kilodalton polypeptide, suggesting a requirement for de novo protein synthesis.     

Harijans and Girijans of Andhra Pradesh: an application of analysis of variance in the study of fertility,mortality and family planning

Research on the Bagatha tribe and the Malas and Madigas in India has been done for economic and social planning purposes in regard to family planning. Bagatha are mostly agricultural people where the nuclear family is prevalent and polygamy is popular as well as cousin marriage. The Madigas and Males (Harijans) are lower caste with the 1st being leather workers and the latter being agricultural helpers. The data was collected by direct interview of 202 tribesmen and 202 caste households with women from 15-49 years of age. The data collected on fertility include live births, child survival rate, fetal wastage, husband and wives education, income, and occupations. On mortality, the number of deaths, age at marriage, number of and intervals of pregnancies. As expected, educated and employed families show healthier and higher levels of fertility especially if the wife is educated. The wife shows more of the responsibility for family planning. The age at marriage and the number of pregnancies appears to have little effect on mortality. In the caste group the education level of the husband has little effect on fertility and again the wife has the primary responsibility in using family planning techniques.     

Phosphoenolpyruvate-dependent protein kinase activity in rat skeletal muscle

Phosphoenolpyruvate-dependent protein kinase activity has been demonstrated in the soluble fraction of rat skeletal muscle. The reaction was not due to the formation of ATP in the incubation mixture. Cyclic AMP, calcium, ATP and a number of phosphate acceptor proteins did not stimulate the reaction. One 32P-labelled protein (Mr 25000) was observed on SDS gels. The phosphorylated protein contained acid stable phosphoserine as a major phosphorylated amino acid. The phosphorylation reaction in crude extracts was not directly proportional to the amount of protein, but typical of a two-component system; i.e., kinase and substrate. The chromatography of soluble proteins on Ultrogel AcA44 separated the phosphate acceptor protein(s) from the phosphoenolpyruvate-dependent protein kinase activity.     

Biochemical Aspects of Parasitism by the Angiosperm Parasites: Host-parasite Interrelationship in Phosphatase Activity

Infection by Cuscuta and Orobanche causes significant losses in dry solids and protein content in host plant or plant part. Changes occur in phosphatase activity towards fructose-1,6-diphosphate at alkaline pH and β-glycerophosphate at acid pH, expressed per mg protein or g fresh tissue. The leaves of all hosts infected by Orobanche show an increase in the alkaline fructosediphosphatase activity, whereas as far as the infection by Cuscuta is concerned the general response is a decrease in the enzyme in the shoots. The alterations in the phosphatase activity towards β-glycerophosphate at acid pH in the shoots are not consistent. However, there is a marked increase in the acid phosphatase activity against β-glycerophosphatase in the roots of the infected hosts. The significance of these findings has been discussed in the light of host-parasite interrelationship.     

Tomato Fruit Carboxypeptidase (Properties,Induction upon Wounding,and Immunocytochemical Localization)

Carboxypeptidase activity was characterized during ripening and wounding of tomato (Lycopersicon esculentum) fruit. The fruit enzyme shares substrate specificity and susceptibility to the inhibitors diisopropyl fluorophosphate and phenylmethylsulfonyl fluoride with other plant carboxypeptidases. The abundance and stability of wound-induced carboxypeptidase were developmentally regulated. Oxidative stress caused by cupric ions impaired the membrane permeability in the slices from pink fruit, resulting in leakage of the carboxypeptidase into the medium and in its redistribution in the cell. The patterns of carboxypeptidase activity did not parallel the cupric ion effect on ethylene levels. Immunogold electron microscopy studies indicated that the fruit carboxypeptidase is associated with electron-dense inclusions in the vacuole.     

Dephosphorylation of photosystem II core proteins is light-regulated in vivo.

A number of photosystem II (PSII)-associated proteins, including D1, D2, CP43 and LHCII, are phosphorylated post-translationally by a membrane-bound, redox-regulated kinase activity. In vitro studies have demonstrated that these proteins can be dephosphorylated by membrane-bound phosphatase activity, reportedly insensitive to light or redox control. We demonstrate here that the PSII core proteins, D1, D2 and CP43, undergo light-stimulated, linear electron-transport-independent dephosphorylation in vivo. The in vivo dephosphorylation of D1 was characterized further and shown to depend upon light intensity, and to occur throughout the visible light spectrum with characteristics most consistent with light absorption by chlorophyll. PSII core protein dephosphorylation in vivo was stimulated by photosystem I (PSI)-specific far-red light, and inhibited by 2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone, an inhibitor of plastoquinol oxidation by the cytochrome b6f complex. Based on these findings, we propose that PSI excitation is involved in regulating dephosphorylation of PSII core proteins in vivo.