Mycobacterium tuberculosis Glucosyl-3-Phosphoglycerate Synthase: Structure of a Key Enzyme in Methylglucose Lipopolysaccharide Biosynthesis

Tuberculosis constitutes today a serious threat to human health worldwide, aggravated by the increasing number of identified multi-resistant strains of Mycobacterium tuberculosis, its causative agent, as well as by the lack of development of novel mycobactericidal compounds for the last few decades. The increased resilience of this pathogen is due, to a great extent, to its complex, polysaccharide-rich, and unusually impermeable cell wall. The synthesis of this essential structure is still poorly understood despite the fact that enzymes involved in glycosidic bond synthesis represent more than 1% of all M. tuberculosis ORFs identified to date. One of them is GpgS, a retaining glycosyltransferase (GT) with low sequence homology to any other GTs of known structure, which has been identified in two species of mycobacteria and shown to be essential for the survival of M. tuberculosis. To further understand the biochemical properties of M. tuberculosis GpgS, we determined the three-dimensional structure of the apo enzyme, as well as of its ternary complex with UDP and 3-phosphoglycerate, by X-ray crystallography, to a resolution of 2.5 and 2.7 Å, respectively. GpgS, the first enzyme from the newly established GT-81 family to be structurally characterized, displays a dimeric architecture with an overall fold similar to that of other GT-A-type glycosyltransferases. These three-dimensional structures provide a molecular explanation for the enzyme's preference for UDP-containing donor substrates, as well as for its glucose versus mannose discrimination, and uncover the structural determinants for acceptor substrate selectivity. Glycosyltransferases constitute a growing family of enzymes for which structural and mechanistic data urges. The three-dimensional structures of M. tuberculosis GpgS now determined provide such data for a novel enzyme family, clearly establishing the molecular determinants for substrate recognition and catalysis, while providing an experimental scaffold for the structure-based rational design of specific inhibitors, which lay the foundation for the development of novel anti-tuberculosis therapies

Functional and informatics analysis enables glycosyltransferase activity prediction

The elucidation and prediction of how changes in a protein result in altered activities and selectivities remain a major challenge in chemistry. Two hurdles have prevented accurate family-wide models: obtaining (i) diverse datasets and (ii) suitable parameter frameworks that encapsulate activities in large sets. Here, we show that a relatively small but broad activity dataset is sufficient to train algorithms for functional prediction over the entire glycosyltransferase superfamily 1 (GT1) of the plant Arabidopsis thaliana. Whereas sequence analysis alone failed for GT1 substrate utilization patterns, our chemical–bioinformatic model, GT-Predict, succeeded by coupling physicochemical features with isozyme-recognition patterns over the family. GT-Predict identified GT1 biocatalysts for novel substrates and enabled functional annotation of uncharacterized GT1s. Finally, analyses of GT-Predict decision pathways revealed structural modulators of substrate recognition, thus providing information on mechanisms. This multifaceted approach to enzyme prediction may guide the streamlined utilization (and design) of biocatalysts and the discovery of other family-wide protein functions

Fungicidal Efficacy of Ammoniacal Copper and Zinc Arsenic Preservatives Tested by Soil-Block Cultures

Three new preservative formulations-copper-zinc-arsenic-additive (CZAA), copper-arsenic-additive (CAA), and zinc-arsenic-additive (ZAA)—were tested in comparison with four other preservatives by soil-block culture on unleached red pine samples using test fungi Coniophora puteana, Poria monticola, and Lenzites trabea.Threshold values (based on retentions of all oxides) of 0.1 pound per cubic foot (1.6 kg/m3) for CAA and 0.2 pound per cubic foot (3.2 kg/m3) for CZAA were comparable with threshold values of the commercial preservatives ammoniacal copper arsenate (ACA) at 0.1 pound per cubic foot (1.6 kg/m3) and eliminated copper arsenate type C (CCA-C) at 0.3 pound per cubic foot (4.8 kg/m3). The ZAA formulation had a relatively high threshold value [0.6 pound per cubic foot (9.6 kg/m3)]. Thresholds based on As2O5 retentions only indicated the fungicidal efficacy in decreasing order: ACA or CAA > CZAA > CCA-C > ZAA.Coniophora puteana (A328, EFPL) was more resistant to all tested preservatives (except ZAA) than the standard strains of Poria monticola and Lenzites trabea

Indoor air quality assessment in an office-library building. Part II - Test results

A detailed investigation of the indoor air quality of a fully air-conditioned eight-story office/library building was carried out. The main purpose of the investigation was to determine the cause(s) of occupants' complaints, which included stuffy air, headaches, eye irritation, prolonged allergic reaction, and a decline in health. Details of the study are presented in two papers. The test plan and the analytical procedures employed are discussed in Part 1 (Shaw et al. 1991). This paper, Part II, presents the results and recommendations for remedial measures in the building.Peer reviewed: YesNRC publication: Ye

Indoor air quality assessment in an office-library building. Part I - Test methods

A detailed investigation of the indoor air quality (IAQ) of a fully air-conditioned eight-story office/library building was carried out. The main purpose of the investigation was to determine the cause(s) of occupants' complaints, which included stuffy air, headaches, eye irritation, a decline in health, and prolonged allergic reaction. Details of the study are presented in two papers. Part I describes the test plan and procedures, which, while developed specifically for this investigation, can be adapted for similar office building studies. Part II presents the study results and recommendations for remedial measures for this building.Peer reviewed: YesNRC publication: Ye

Indoor Air Quality Assessment in Building M-55

An investigation of the air quality in this building was requested by the NRC Safety Officer. The main purpose of the investigation was to determine whether there is a health hazard to M-55 staff or visitors, and if so, to provide recommendations for correcting the problem. The events leading to this request included (1) a formal complaint of prolonged allergic reaction and decline in health by a staff member working on the first floor, and (2) several verbal complaints of headaches, eye irritations, and stuffy and uncomfortably dry air in the stacks area by the photocopying staff on the fifth and sixth floors. Since 1981, two ad hocstudies have been conducted to identlfy the causes of the complaints. As the results of these studies wereinconclusive, a thorough study was conducted to assess the air quality of this building.L'Agent de s\ue9curit\ue9 du CNRC a demand\ue9 la tenue d'une enqu\ueate sur la qualit\ue9 de l'air \ue0 l'int\ue9rieur de l'\ue9difice M-55. Cette enqu\ueate avait pour but principal de d\ue9terminer s'il existe un risque pour la sant\ue9 du personnel ou des visiteurs de ce b\ue2timent, et, le cas \ue9ch\ue9ant, de fournir des recommandations en vue d'y rem\ue9dier. Les \ue9v\ue9nements \ue9tant \ue0 l'origine de cette demande sont les suivants: 1) une plainte officielle, \ue9mise par un membre du personnel travaillant au rez-de-chauss\ue9e, all\ue9guant souffrir d'une r\ue9action allergique prolong\ue9e et \ue9prouver une moins bonne sant\ue9 qu'auparavant; et 2) plusieurs plaintes verbales, soumises par le personnel de la photocopie concernant des c\ue9phal\ue9es, de l'irritation aux yeux et un air vici\ue9 ou malsain dans la zone des chemin\ue9es, aux cinqui\ue8me et sixi\ue8me \ue9tages. Depuis 1981, deux (2) \ue9tudes sp\ue9ciales ont \ue9t\ue9 men\ue9es dans le but d'identifier les causes de ces probl\ue8mes. Comme les r\ue9sultats de ces \ue9tudes ne se sont pas r\ue9v\ue9l\ue9s concluants, on a mis en ?uvre une \ue9tude approfondie ayant pour objet l'\ue9valuation de la qualit\ue9 de l'air dans ce b\ue2timent.Peer reviewed: NoNRC publication: Ye