Role of PheE15 gate in ligand entry and nitric oxide detoxification function of Mycobacterium tuberculosis truncated hemoglobin N

The truncated hemoglobin N, HbN, of Mycobacterium tuberculosis is endowed with a potent nitric oxide dioxygenase (NOD) activity that allows it to relieve nitrosative stress and enhance in vivo survival of its host. Despite its small size, the protein matrix of HbN hosts a two-branched tunnel, consisting of orthogonal short and long channels, that connects the heme active site to the protein surface. A novel dual-path mechanism has been suggested to drive migration of O(2) and NO to the distal heme cavity. While oxygen migrates mainly by the short path, a ligand-induced conformational change regulates opening of the long tunnel branch for NO, via a phenylalanine (PheE15) residue that acts as a gate. Site-directed mutagenesis and molecular simulations have been used to examine the gating role played by PheE15 in modulating the NOD function of HbN. Mutants carrying replacement of PheE15 with alanine, isoleucine, tyrosine and tryptophan have similar O(2)/CO association kinetics, but display significant reduction in their NOD function. Molecular simulations substantiated that mutation at the PheE15 gate confers significant changes in the long tunnel, and therefore may affect the migration of ligands. These results support the pivotal role of PheE15 gate in modulating the diffusion of NO via the long tunnel branch in the oxygenated protein, and hence the NOD function of HbN

Clinical characteristics of vulnerable populations hospitalized and diagnosed with COVID-19 in Buenos Aires, Argentina

There is not in Argentina publications regarding the presentation of patients with COVID-19 requiring hospitalized and emergency care in vulnerable populations (lower incomes and less education tend at greater risk for poor health status and healthcare access), and it has few reports in developing countries. The objective is to determine whether in the care of vulnerable patients, to succeed against COVID-19, multiple public health tools and interventions will be needed to minimize morbidity and mortality. The study is a prospective cohort investigation of patients with lab-confirmed COVID-19, who required to any of the Health Centers response from April 8, 2020, to August 18, 2020. In Buenos Aires Metropolitan Area (AMBA), April 8, 2020 the virus was identified in patients hospitalized in the "Southeast Network" (SN), AMBA. SN covering an area of 661 square kilometers, with 1.8 million inhabitants residing in urban, and rural areas. A total of 14 health centers with different levels of care complexity provide care to patients in the region. The information of each patient with COVID-19 evaluated by SN, was incorporated in an Epidemiological Dashboard. The investigation was designed and reported with consideration of observational studies in epidemiology. We describe the hospitals presentation and care of persons who required SN response and were ultimately diagnosed with COVID-19. From April 8, 2020, to August 18, 2020, were included 1495 patients with lab-confirmed COVID-19 in SN. A total of 58% patients were men, and the mean age (SD) was 48.9 (15.59) years. Eighty one percent patients with pre-existing diseases, most frequent hypertension and diabetes, but hypertension, chronic lung disease, and cardiovascular disease presented higher risk. A total of 13% were hospitalized in Intensive Therapy Unit. The mortality of the cohort was 9.77%. Mortality was higher for patients aged 65 or more (OR 5.09), and for those had some pre-existing disease (OR 2.61). Our observations are consistent with reports demonstrating older persons, and those with comorbidities have the highest risk of mortality related to COVID-19. However, unlike other reports from developed or some developing countries, the mortality in our study is lower. This finding may be related to age of our cohort is younger than other published. Also, the health system was able to respond to the demand.Fil: Yacobitti, A.. Provincia de Buenos Aires. Ministerio de Salud. Hospital Alta Complejidad en Red El Cruce Dr. Néstor Carlos Kirchner Samic; ArgentinaFil: Otero, L.. Provincia de Buenos Aires. Ministerio de Salud. Hospital Alta Complejidad en Red El Cruce Dr. Néstor Carlos Kirchner Samic; ArgentinaFil: Doldan Arrubarrena, V.. Provincia de Buenos Aires. Ministerio de Salud. Hospital Alta Complejidad en Red El Cruce Dr. Néstor Carlos Kirchner Samic; ArgentinaFil: Arano, J.. Provincia de Buenos Aires. Ministerio de Salud. Hospital Alta Complejidad en Red El Cruce Dr. Néstor Carlos Kirchner Samic; ArgentinaFil: Lage, S.. Provincia de Buenos Aires. Ministerio de Salud. Hospital Alta Complejidad en Red El Cruce Dr. Néstor Carlos Kirchner Samic; ArgentinaFil: Silberman, M.. Provincia de Buenos Aires. Ministerio de Salud. Hospital Alta Complejidad en Red El Cruce Dr. Néstor Carlos Kirchner Samic; ArgentinaFil: Zubieta, M.. Provincia de Buenos Aires. Ministerio de Salud. Hospital Alta Complejidad en Red El Cruce Dr. Néstor Carlos Kirchner Samic; ArgentinaFil: Erbetta, I.. Provincia de Buenos Aires. Ministerio de Salud. Hospital Alta Complejidad en Red El Cruce Dr. Néstor Carlos Kirchner Samic; ArgentinaFil: Danei, P.. Provincia de Buenos Aires. Ministerio de Salud. Hospital Alta Complejidad en Red El Cruce Dr. Néstor Carlos Kirchner Samic; ArgentinaFil: Baeck, G.. Hospital Mi Pueblo; ArgentinaFil: Vallejos, V.. No especifíca;Fil: Cavalli, F.. No especifíca;Fil: Calderón, N.. Gobierno de la Provincia de Buenos Aires. Hospital Zonal General de Agudos Doctor Lucio Melendez.; ArgentinaFil: Di Gregorio, M.. Gobierno de la Provincia de Buenos Aires. Hospital Zonal General de Agudos Doctor Lucio Melendez.; ArgentinaFil: Hernandez, V.. Hospital Dr. Arturo Oñativia - Salta Capital.; ArgentinaFil: Bruno, D.. Hospital Dr. Arturo Oñativia - Salta Capital.; ArgentinaFil: Rodera, B.. Municipalidad de Quilmes (buenos Aires). Hospital Zonal General de Agudos Doctor Isidoro Iriarte.; ArgentinaFil: Macherett, I.. Municipalidad de Quilmes (buenos Aires). Hospital Zonal General de Agudos Doctor Isidoro Iriarte.; ArgentinaFil: Parisi, M.. Municipalidad de Quilmes (buenos Aires). Hospital Zonal General de Agudos Doctor Isidoro Iriarte.; ArgentinaFil: Gallastegui, M.. Municipalidad de Quilmes (buenos Aires). Hospital Zonal General de Agudos Doctor Isidoro Iriarte.; ArgentinaFil: Paz, A.. Municipalidad de Quilmes (buenos Aires). Hospital Sub Zonal Materno Infantil Doctor Eduardo Oller.; ArgentinaFil: Bernardi, R.. No especifíca;Fil: Azcárate, S.. Gobierno de la Provincia de Buenos Aires. Hospital Provincial Evita Pueblo.; ArgentinaFil: Hraste, A.. Gobierno de la Provincia de Buenos Aires. Hospital Provincial Evita Pueblo.; ArgentinaFil: Caridi, Délida Inés. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Cálculo; ArgentinaFil: Boechi, Leonardo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Cálculo; ArgentinaFil: Salgado, P.. Universidad de Buenos Aires. Rectorado. Instituto de Investigaciones en Salud Pública; ArgentinaFil: Kochen, Sara Silvia. Gobierno de la Provincia de Buenos Aires. Hospital de Alta Complejidad Cuenca Alta Doctor Nestor Carlos Kirchner.; Argentina. Universidad Nacional Arturo Jauretche; Argentina. Universidad de Buenos Aires; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Structural determinants of ligand migration in Mycobacterium tuberculosis truncated hemoglobin O

Mycobacterium tuberculosis is the causative agent of human tuberculosis, one of the most prevalent infectious diseases in the world. Its genome hosts the glbN and glbO genes coding for two proteins, truncated hemoglobin N (trHbN) and truncated hemoglobin O (trHbO), that belong to different groups (I and 11, respectively) of the recently discovered trHb family of hemeproteins. The different expression pattern and kinetics rates constants for ligand association and NO oxidation rate suggest different functions for these proteins. Previous experimental and theoretical studies showed that, in trHbs, ligand migration along the internal tunnel cavity system is a key issue in determining the ligand-binding characteristics. The X-ray structure of trHbO has been solved and shows several internal cavities and secondary-docking sites. In this work, we present an extensive investigation of the tunnel/cavity system of M. tuberculosis trHbO by means of computer-simulation techniques. We have computed the free-energy profiles for ligand migration along three found tunnels in the oxy and deoxy w.t. and mutant trHbO proteins. Our results show that multiple-ligand migration paths are possible and that several conserved residues such as TrpG8 play a key role in the ligand-migration regulation

Protonation of histidine 55 affects the oxygen access to heme in the alpha chain of the hemoglobin from the Antarctic fish Trematomus bernacchii.

The Root effect describes the drastic drop of oxygen affinity and loss of cooperativity at acidic pH expressed in the hemoglobins (Hb) of certain fish. The comparison between the deoxy structures of the Root effect Hb from the Antarctic fish Trematomus bernacchii (HbTb) at different pHs (pH = 6.2 and pH = 8.4) shows that the most significant differences are localized at the CDα region, where a salt bridge between Asp48 and His55 breaks during the low-to-high pH transition. In order to shed light on the relationship between pH, CDα loop structure and dynamics, and oxygen access to the active site in the alpha chain of HbTb, different computer simulation techniques were performed. Our results highlight the importance of the protonation of His55 in regulating oxygen access, underscoring its pivotal role in the structural and functional properties of HbTb. These data provide further support to the hypothesis that this residue might contribute to the release of Root protons in HbTb and underline the fact that an efficient transport of molecular oxygen in Hbs relies on a subtle balance of tertiary structure and protein conformational flexibility

Role of heme distortion on oxygen affinity in heme proteins: The protoglobin case

The chemical properties of heme proteins largely reflect the electronic properties of their heme group. Often, the porphyrin ring of the heme exhibits significant distortions from its isolated structure, but the impact of these distortions on the chemical properties of the heme is yet uncertain. A systematic study focused on the effects of the distortion of the macrocycle on the binding affinity for oxygen is presented. The results show that out-of-plane distortions decrease the binding affinity, while in-plane distortions can increase or decrease it. Among in-plane distortions, only the breathing mode, which involves the symmetric compression-expansion of the porphyrin ring, strongly modulates the binding affinity. These findings shed light into the peculiar binding affinity of Methanosarcina acetivorans protoglobin, a protein that contains a highly distorted heme. Overall, the results highlight that in-plane distortions might be exploited by certain classes of heme proteins to modulate the ligand affinity. \ua9 2010 American Chemical Society

Structural flexibility of the heme cavity in the cold-adapted truncated hemoglobin from the Antarctic marine bacterium Pseudoalteromonas haloplanktis TAC125

Truncated hemoglobins build one of the three branches of the globin protein superfamily. They display a characteristic two-on-two \u3b1-helical sandwich fold and are clustered into three groups (I, II and III) based on distinct structural features. Truncated hemoglobins are present in eubacteria, cyanobacteria, protozoa and plants. Here we present a structural, spectroscopic and molecular dynamics characterization of a group-II truncated hemoglobin, encoded by the PSHAa0030 gene from Pseudoalteromonas haloplanktis TAC125 (Ph-2/2HbO), a cold-adapted Antarctic marine bacterium hosting one flavohemoglobin and three distinct truncated hemoglobins. The Ph-2/2HbO aquo-met crystal structure (at 2.21 \uc5 resolution) shows typical features of group-II truncated hemoglobins, namely the two-on-two \u3b1-helical sandwich fold, a helix \u3a6 preceding the proximal helix F, and a heme distal-site hydrogen-bonded network that includes water molecules and several distal-site residues, including His(58)CD1. Analysis of Ph-2/2HbO by electron paramagnetic resonance, resonance Raman and electronic absorption spectra, under varied solution conditions, shows that Ph-2/2HbO can access diverse heme ligation states. Among these, detection of a low-spin heme hexa-coordinated species suggests that residue Tyr(42)B10 can undergo large conformational changes in order to act as the sixth heme-Fe ligand. Altogether, the results show that Ph-2/2HbO maintains the general structural features of group-II truncated hemoglobins but displays enhanced conformational flexibility in the proximity of the heme cavity, a property probably related to the functional challenges, such as low temperature, high O2 concentration and low kinetic energy of molecules, experienced by organisms living in the Antarctic environment

High protein structural flexibility of a truncated hemoglobin from an antarctic cold-adapted bacterium

Fil:Boechi, L. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.Fil:Estrin, D.A. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina