menaquinone. Deletion mutants have reduced oxygen consumptionrates and electron transport efficiency, although membrane integrity,cellular ATP levels and rates of ATP synthesis are unaltered as arebacterial growth rates. However, in vitro infection studies using J774A.1cells and theM. tuberculosis Rv0561c deletionmutant demonstrated thatthe mutant is unable to survive in macrophage-like cells. Thus, Rv0561crepresents a novel, contextually essential enzyme that is a potentialdrug target inM. tuberculosis. Funded by NIH/NIAID grant # AI049151.

doi:10.1016/j.bbabio.2014.05.034

S12.L4

Structure of the trypanosomal alternative oxidase: Opportunitiesfor rational drug design to treat trypanosomiasisAnthony L. Moorea, Luke Younga, Benjamin Maya, Tomoo Shibab,Daniel Ken Inaokac, Shigeharu Haradab, Kiyoshi KitacaBiochemistry and Molecular Sciences, School of Life Sciences, Universityof Sussex, Falmer, Brighton BN1 9QG, United KingdombDepartment of Applied Biology, Graduate School of Science and Technology,Kyoto Institute of Technology, Kyoto 606-8585, JapancDepartment of Biomedical Chemistry, Graduate School of Medicine,The University of Tokyo, Tokyo 113-0033, JapanE-mail address: a.l.moore@sussex.ac.uk

In addition to haem copper oxidases, all higher plants, some algae,yeasts, molds, metazoans, and pathogenic microorganisms such asTrypanosoma brucei contain an additional terminal oxidase, thecyanide-insensitive alternative oxidase (AOX). AOX is a diiron carbox-ylate protein that catalyzes the four-electron reduction of dioxygen towater by ubiquinol. In T. brucei, a parasite that causes human Africansleeping sickness, AOX plays a critical role in the survival of the parasitein its bloodstream form. Because AOX is absent from mammals, thisprotein represents a unique and promising therapeutic target. This talkwill discuss recent crystal structures of the trypanosomal alternativeoxidase obtained in the absence and presence of specific inhibitors. Allstructures reveal that the oxidase is a homodimer with the non-haemdiiron carboxylate active site buried within a four-helix bundle. CAVERprotein analysis reveals that there are two hydrophobic cavities permonomer. One cavity, which is perpendicular to themembrane surface,binds both inhibitors and substratewithin 4 Å of the active sitewhereasthe second cavity, which is parallel to the membrane surface and alsolinks with the active-site, acts as an oxygen/H2O channel. We suggestthat detailed knowledge of the nature of the inhibitor/substrate cavitywill lead to a greater rational design of anti-trypanosomal drugs.

doi:10.1016/j.bbabio.2014.05.035

S12. O1

Cancer energy metabolism under hypoglycemiaRafaelMoreno Sáncheza, AlvaroMarinHernandezb, Sayra Lopez Ramireza,Juan Carlos Gallardo Pareza, Emma Saavedraa, Sara Rodriguez EnriquezaaInstituto Nacional Cardiologia, MexicobInstituto Nacional de Cardiologia, MexicoE-mail address: rafael.moreno@cardiologia.org.mx

Most studies on cancer metabolism have been carried out in cellscultured with high glucose (25 mM; hyperglycemia). However, theglucose concentrations range from 5 mM in well blood-irrigatedareas to 0.25–2.5 mM in areas within solid tumors that are awayfrom blood vessels. These low glucose levels may induce changes in

the cancer cell behavior. Indeed, it is well documented that culturingwith low glucose promotes substantial variations in the mRNA levelsof a multitude of genes. However, no evidences have been so farprovided about the impact that such transcriptional remodelinghas on the protein contents and activities of enzymes/transportersand, perhaps more importantly, whether these changes significantlymodify pathway fluxes and cellular functions.

In the present study, it was analyzed that the effect of hypoglycemiaon the contents of glycolytic and mitochondrial proteins, activities ofenzymes/transporters and fluxes of glycolysis and oxidative phosphor-ylation (OxPhos) in HeLa andMCF-7 tumor cells. One day hypoglycemia(2.5 mM initial glucose) induced increased protein levels of glucosetransporters (GLUT) 1 and 3 (2–3 fold) and hexokinase I (HK; 2.3-fold),compared to hyperglycemia. Remarkably, these increases were notaccompanied by increases in the total cellular activities (i.e. Vmax) ofGLUT and HK; instead, increased affinity of these activities for glucosesurged, which may explain the 2-fold increased glycolytic flux underhypoglycemia. Therefore, a change towards greater catalytically ef-ficient isoforms of two of the main controlling steps sufficed to induceincreased glycolytic flux.

Hypoglycemia also induced a decrease in the pyruvate dehydroge-nase content and increase in the respiratory complex I, with no variationin those of isocitrate dehydrogenase and 2-oxoglutarate dehydrogenase.The activities ofmalate dehydrogenase, fumarase and citrate synthase, aswell as the OxPhos flux (i.e., rate of O2 consumption sensitive tooligomycin) and the electrical membrane potential, were not modifiedby hypoglycemia. Hence, the contribution to the ATP supply by glycolysisincreased from 27–35% under hyperglycemia to 44–70% under hypogly-cemia, depending on the cancer cell type, and noting that OxPhoscontribution was still significant. Therefore, the results indicated that, toeffectively diminish the accelerated cancer cell growth, the two energymetabolism pathways should be targeted simultaneously.

doi:10.1016/j.bbabio.2014.05.036

S12.O2

Functional and structural characterization of a Staphyloccocusaureus flavohemoglobinMyriam MoussaouiILaboratoire Chimie Physique, FranceE-mail address: moussaoui.myriam@gmail.com

Flavohemoglobins (flavoHbs) play a key role in bacterial resistanceto nitrosative stress and NO signaling modulation. Typically, flavoHbscontains three domains: an N-terminal globin domain which harborsa single heme type b and a C-terminal ferredoxin reductase-like FAD-and NAD-binding module. In this presentation, we cloned, expressedand characterized the flavoHb from the opportunistic pathogen,Staphylococcus aureus. The high amino acid sequence homology withSaccharomyces cerevisaewas used to build a model structure by homol-ogymodeling showing structural similaritieswith those of other knownflavoHbs. Interestingly this high sequence homology did not correlatewith the enzymatic and kinetic properties which are much similar tothose of Escherichia coli. In vitro and aerobically, the enzyme acceptscytochrome c and oxygen as substrate. Based on this feature, weshowed that in Staphylococcus aureus and Ralstonia eutropha flavoHbsthe preferences for cytochrome c and dioxygen depending on thepresence of NO dioxygenase inhibitors are different and this is deter-mined by the inhibitor chemical composition. To make progress inunderstanding the catalyticmechanism of flavoHbswe investigated theenzyme properties, the effect of azole antibiotics and the structure-function relationship in comparison to the well-known flavoHbs fromthe non-pathogenic bacteria. The mutation of key residues situated in

Abstracts e127