De-N-glycosylation activities are found in every part of the tomato plant

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Combined Experimental and Computational Approaches Reveal Distinct pH Dependence of Pectin Methylesterase Inhibitors.

The fine-tuning of the degree of methylesterification of cell wall pectin is a key to regulating cell elongation and ultimately the shape of the plant body. Pectin methylesterification is spatiotemporally controlled by pectin methylesterases (PMEs; 66 members in Arabidopsis [Arabidopsis thaliana]). The comparably large number of proteinaceous pectin methylesterase inhibitors (PMEIs; 76 members in Arabidopsis) questions the specificity of the PME-PMEI interaction and the functional role of such abundance. To understand the difference, or redundancy, between PMEIs, we used molecular dynamics (MD) simulations to predict the behavior of two PMEIs that are coexpressed and have distinct effects on plant development: AtPMEI4 and AtPMEI9. Simulations revealed the structural determinants of the pH dependence for the interaction of these inhibitors with AtPME3, a major PME expressed in roots. Key residues that are likely to play a role in the pH dependence were identified. The predictions obtained from MD simulations were confirmed in vitro, showing that AtPMEI9 is a stronger, less pH-independent inhibitor compared with AtPMEI4. Using pollen tubes as a developmental model, we showed that these biochemical differences have a biological significance. Application of purified proteins at pH ranges in which PMEI inhibition differed between AtPMEI4 and AtPMEI9 had distinct consequences on pollen tube elongation. Therefore, MD simulations have proven to be a powerful tool to predict functional diversity between PMEIs, allowing the discovery of a strategy that may be used by PMEIs to inhibit PMEs in different microenvironmental conditions and paving the way to identify the specific role of PMEI diversity in muro

Coenzyme Q10 deficiencies in neuromuscular diseases

páginas, 2 figuras, 1 tabla. Editado por Carmen Espinós, Vicente Felipo y Francesc Palau.Coenzyme Q (CoQ) is an esssential component of the respiratory chain but also participates in other mitochondrial functions such as regulation of the transition pore and uncoupling proteins. Furthermore, this compound is a specific substrate for enzymes of the fatty acids β-oxidation pathway and pyrimidine nucleotide biosynthesis. Furthermore, CoQ is an antioxidant that acts in all cellular membranes and lipoproteins. A complex of a least ten nuclear (COQ) genes encoded proteins synthesis CoQ but its regulation is unknown. Since 1989, a growing number of patients with multsystemic mitochondrial disorders and neuromuscular disorders showing deficiencies of CoQ have been identified. CoQ deficiency caused by mutation(s) in any of the COQ genes in designated primary deficiency. Other patients have displayed other genetic defects independent on the CoQ biosynthesis pathway, and are considered to have secondary deficiencies. This review updates the clinical and molecular aspects of both types of CoQ deficiencies and proposes new approaches to understanding their molecular bases.This work has been partially supported by the European Union contract LSHB-CT-2004-005151 and the NIH grant 1R01HD057543-01.Peer reviewe