Unique Biochemical Features of the Cytokinetic Protein FtsZ of Mycobacteria

FtsZ, the bacterial cytokinetic protein, a structural homologue of mammalian β-tubulin, is present in bacteria of diverse genera, including mycobacteria. The FtsZ protein of Mycobacterium tuberculosis (M. tuberculosis FtsZ), the causative agent of tuberculosis, is the most studied among the mycobacterial FtsZ proteins as it is a potential anti-tuberculosis drug target. M. tuberculosis FtsZ possesses many unique biochemical features, which include slow polymerisation kinetics, presence of charged amino acids in the C-terminal domain that interacts with a variety of other cell division proteins, and the presence of specific amino acids at unique locations that makes it distinct from the FtsZ of other mycobacterial species and of other bacterial genera. On the other hand, although the FtsZ of Mycobacterium leprae (M. leprae FtsZ), the causative agent of leprosy, shows high level of conservation with M. tuberculosis FtsZ, it has biochemical properties that are very different from those of M. tuberculosis FtsZ due to the difference in specific amino acid residues at critical locations on the protein. The present review focuses on these structural features of M. tuberculosis FtsZ and M. leprae FtsZ, as studied by others and by us, in comparison to those of the FtsZ of other mycobacterial species and of other bacterial genera

An improved immune algorithm with parallel mutation and its application

The objective of this paper is to design a fast and efficient immune algorithm for solving various optimization problems. The immune algorithm (IA), which simulates the principle of the biological immune system, is one of the nature-inspired algorithms and its many advantages have been revealed. Although IA has shown its superiority over the traditional algorithms in many fields, it still suffers from the drawbacks of slow convergence and local minima trapping problems due to its inherent stochastic search property. Many efforts have been done to improve the search performance of immune algorithms, such as adaptive parameter setting and population diversity maintenance. In this paper, an improved immune algorithm (IIA) which utilizes a parallel mutation mechanism (PM) is proposed to solve the Lennard-Jones potential problem (LJPP). In IIA, three distinct mutation operators involving cauchy mutation (CM), gaussian mutation (GM) and lateral mutation (LM) are conditionally selected to be implemented. It is expected that IIA can effectively balance the exploration and exploitation of the search and thus speed up the convergence. To illustrate its validity, IIA is tested on a two-dimension function and some benchmark functions. Then IIA is applied to solve the LJPP to exhibit its applicability to the real-world problems. Experimental results demonstrate the effectiveness of IIA in terms of the convergence speed and the solution quality

The effect lateral interactions: a biophysical characterization of E. coli FtsZ lateral mutants

Tesis doctoral inédita leída en la Universidad Autónoma de Madrid, Facultad de Ciencias, Departamento de Física de la Materia Condensada. Fecha de lectura: 27-06-2014La bacteria Escherichia coli (E. coli) es uno de los organismos que se utiliza para estudiar la división celular bacteriana dada su fácil reproducción y crecimiento en laboratorios. Esta bacteria, del tipo Gramnegativa, ha sido investigada exhaustivamente en los últimos veinte años intentando entender los mecanismos de su división celular. Muchas de las bacterias Gram-negativas son patógenas por lo que desarrollar nuevos fármacos capaces de controlar su proliferación es importante para curar infecciones. Gracias al meticuloso estudio realizado por varios grupos de investigación, se han identificado las proteínas y genes involucrados en la división celular de E. coli. Un complejo macromolecular constituido por al menos 10 proteínas esenciales, y otras 15 proteínas accesorias, es el responsable de dividir la bacteria. Este complejo de proteínas altamente dinámico, llamado divisoma, debe ensamblarse en el sitio donde se producirá la división de la célula bacteriana. La división se inicia con la formación del proto-anillo. Este anillo lo constituyen polímeros de la proteína FtsZ (el anillo Z) y dos proteínas asociadas a la membrana celular interna: FtsA que interacciona a través de una hélice anfipática, y ZipA que se encuentra integrada a través de una única hélice transmembrana. Dado que FtsZ se halla soluble en el citoplasma bacteriano, los polímeros necesitan interaccionar al menos con FtsA o ZipA para ser anclados a la membrana interna a través de su interacción con el carboxi-terminal de FtsZ. También se han identificado otras proteínas accesorias, aunque no esenciales, que se localizan en el sitio de división y contribuyen a la estabilización del anillo Z antes de iniciarse la constricción de ambas paredes celulares, interna y externa. FtsZ es una proteína capaz de polimerizar uniendo dos monómeros por medio de la incorporación de una molécula de nuclótido GTP. Inmediatamente después de la unión de GTP se produce la hidrólisis del nucleótido en GDP que se intercambia nuevamente por otro GTP manteniendo la unión entre monómeros estable. Esta actividad GTPasa sumada al rápido intercambio de monómeros dentro de un polímero hace que FtsZ muestre in vitro un alto polimorfismo y dinamismo bajo distintas condiciones de polimerización. Mediante técnicas de microscopía, tales como microscopía electrónica o microscopía de fuerzas atómicas, se han observado filamentos simples, dobles, curvos, rectos, circulares, en forma de espiral y planchas de polímeros asociados lateralmente, así como superestructuras del tipo cintas y toroides Dado que FtsZ exhibe in vitro este extenso polimorfismo, las preguntas inmediatas que surgen son ¿cómo se encuentran dispuestos estos polímeros dentro del anillo Z? y ¿cómo es el mecanismo de generación de fuerza necesaria para la constricción de la célula bacteriana? Para responder a estas preguntas se han realizado diversos estudios tanto in vivo como in vitro, y se han propuesto diferentes modelos de organización de los polímeros de FtsZ y de posibles mecanismos generadores de fuerza. Experimentos in vivo han mostrado que mutaciones en ciertos amino ácidos de FtsZ alteran la funcionalidad de la proteína inhibiendo la división de E. coli. Sorprendentemente, todas las mutaciones de FtsZ dirigidas a las zonas de contacto lateral entre polímeros han impedido que la bacteria se divida indicando así la importancia de las interacciones laterales para su división. A partir de datos experimentales in vitro se han propuesto diferentes modelos matemáticos de mecanismos posibles para que los filamentos de FtsZ sean contráctiles. Estos modelos se basan en cambios en la curvatura de la unión entre monómeros debido a la hidrólisis del nucleótido, interacciones laterales o restricciones en la torsión natural del filamento según su anclaje a la membrana. A pesar del extenso trabajo in vitro y del avance de la microscopía de alta resolución in vivo, no se ha llegado a un consenso sobre la disposición de los polímeros de FtsZ dentro del anillo de división así como del mecanismo molecular generador de la fuerza constrictiva. Se han propuesto como aspectos relevantes para la constricción a la curvatura y a las interacciones laterales de los filamentos de FtsZ. En esta tesis nos proponemos explorar in vitro el comportamiento de dos mutantes laterales no funcionales de FtsZ descritos previamente por Shin et al. [Shin et al., 2013], y compararlo con el de la proteína nativa mediante un sistema reconstituido en superficies in vitro. Queremos identificar qué características del comportamiento in vitro de estos dos mutantes puede asociarse a su no funcionalidad in vivo. Para caracterizar el efecto de estas mutaciones disponemos de dos técnicas biofísicas de caracterización en superficie: Microscopía de fuerzas atómicas (AFM) y Microbalanza de cuarzo (QCM). Mediante AFM estudiaremos cómo estas mutaciones laterales de FtsZ afectan la forma y dinamismo de los polímeros en mica, así como la formación de agregados en mica y en bicapas lipídicas ancladas, cuando estos filamentos están unidos a través de ZipA. Con QCM cuantificaremos la interacción de FtsZ y ZipA en bicapas lipídicas ancladas a superficies planas para compararla con las medidas disponibles en solución.Escherichia coli (E. coli) bacterium is one of the organisms used to study bacterial cell division given its easy grow and proliferation in laboratories. This Gram-negative bacterium has been studied extensively during the last two decades aiming to understand the mechanisms of its cell division. Many Gram-negative bacteria are pathogens and to develop new compounds to control their proliferation is important to cure infections. From the meticulous research made by several groups, the proteins and genes involved in E. coli cell division have been identified. A macromolecular complex is the responsible for dividing the bacterial cell, composed by at least 10 essential proteins and other 15 accessory proteins. This highly dynamic protein complex, the divisome, must assemble at the cell division site. The bacterial cell division starts with the formation of a proto-ring. This ring is constituted by polymers of the protein FtsZ (the Z-ring) and two membrane associated proteins: FtsA that interacts through an amphipathic helix, and ZipA a bitopic protein integrated into the membrane with a single transmembrane helix. FtsZ is a cytoplasmic protein, therefore, its polymers need to interact with at least FtsA or ZipA to be anchored to the bacterium inner membrane through their interaction with the C-terminus of FtsZ. Other proteins, although not essential, have been identified to localize at the division site that contribute to stabilize the Z-ring before the constriction of both inner and outer cellular walls begins. FtsZ is a protein able to polymerize by binding two monomers incorporating a molecule of nucleotide GTP. Immediately after the binding of a GTP, the nucleotide is hydrolyzed into GDP and it is interchanged by another GTP molecule stabilizing the bond between monomers. This GTPase activity in addition to a fast exchange of monomers within a polymer makes FtsZ displays a high polymorphism and dynamism in vitro. By means of electron microscopy and atomic force microscopy techniques it has been observed FtsZ single filaments, double, curved, straight, circular, spiral and sheets where polymers are associated laterally, as well as superstructures like ribbons and toroids. Given this extensive FtsZ in vitro polymorphism the immediate questions that arise are how are these polymers arranged within the Zring? and how is the force generating mechanism needed for the constriction of the bacterial cell? To answer these questions several studies have been made in vitro, and different models have been proposed for the organization of the FtsZ polymers and possible force generator mechanisms In vivo experiments have shown that mutations on certain amino acids of FtsZ alter its functionality preventing E. coli bacterium from dividing. Surprisingly, all site-directed mutations to the lateral contact zones between polymers are non-functional indicating the importance of these lateral interactions for bacterial cell division. From in vitro experiments, there have been proposed several mathematical models for the mechanisms in order to have contractile FtsZ polymers. These models are based on changes in curvature induced by the nucleotide hydrolysis, lateral interactions or restrictions on the filament natural torsion depending on its anchoring to the membrane. In spite of the extensive work in vitro and the advance of the high resolution microscopy techniques, there have been no consensus about the arrangement of the FtsZ polymers within the division ring nor the molecular mechanism able to generate the constrictive force. Both lateral interactions and curvature of the FtsZ filaments have been proposed as relevant for constriction. On this thesis we want to explore in vitro the behavior of two non-functional FtsZ lateral mutants early described by Shin et al. [Shin et al., 2013] and compare them with that of the native protein by means of a reconstituted systems on surfaces. We want to identify which characteristics in vitro for these two mutants can be associated to their non functionality in vivo. To characterize the effect of these mutations we will use two biophysical techniques on surfaces: Atomic force microscopy (AFM) and Quartz Crystal Microbalance (QCM). With AFM we will study how these mutations affect the shape and dynamism of the polymers on mica, and the formation of bundles on mica and supported lipid bilayers when these polymers are anchored through ZipA. With QCM we will quantify the interaction between FtsZ and ZipA on planar lipid bilayers comparing them to the reported values in solutio

Study Of Ingaas Ldmos For Power Conversion Applications

In this work an n-channel In0.65Ga0.35As LDMOS with Al2O3 as gate dielectric is investigated. Instead of using traditional Si process for LDMOS, we suggest In0.65Ga0.35As as substitute material due to its higher electron mobility and its promising for power applications. The proposed 0.5-µm channel-length LDMOS cell is studied through device TCAD simulation tools. Due to different gate dielectric, comprehensive comparisons between In0.65Ga0.35As LDMOS and Si LDMOS are made in two ways, structure with the same cross-sectional dimension, and structure with different thickness of gate dielectric to achieve the same gate capacitance. The on-resistance of the new device shows a big improvement with no degradation on breakdown voltage over traditional device. Also it is indicated from these comparisons that the figure of merit(FOM) Ron·Qg of In0.65Ga0.35As LDMOS shows an average of 91.9% improvement to that of Si LDMOS. To further explore the benefit of using In0.65Ga0.35As LDMOS as switch in power applications, DC-DC buck converter is utilized to observe the performance of LDMOS in terms of power efficiency. The LDMOS performance is experimented with operation frequency of the circuit sweeping in the range from 100 KHz to 100 MHz. It turns out InGaAs LDMOS is good candidate for power applications

Human Resources Management Audit To Assess The Effectiveness Of Employee At Pt. Janti Sarana Material Beton Malang

Penelitian ini mengenai audit manajemen fungsi sumber daya manusia pada PT. Janti Sarana Material Beton Malang bertujuan untuk mengetahui efektivitas fungsi sumber daya manusia yang diterapkan perusahaan. Ruang lingkup penelitian adalah sembilan fungsi sumber daya manusia yang terdiri dari : fungsi perencanaan SDM, fungsi rekrutmen, fungsi seleksi dan penempatan, fungsi pelatihan dan pengembangan, fungsi penilaian kinerja, fungsi perencanaan dan pengembangan karir, fungsi kompensasi dan balas jasa, fungsi keselamatan dan kesehatan kerja dan fungsi pemutusan hubungan kerja dan pemensiunan. Peneliti menggunakan pendekatan kualitatif deskriptif. Data dari penelitian ini diperoleh dengan cara wawancara, observasi, serta dokumentasi. Hasil penelitian menunjukkan, dari sembilan fungsi sumber daya manusia, terdapat 5 fungsi sumber daya manusia yang tidak efektif, yaitu perencanaan sumber daya manusia, seleksi, orientasi dan penempatan, pelatihan dan pengembangan, penilaian kinerja dan jaminan keamanan dan kesehatan karyawa

Application of metaheuristic and deterministic algorithms for aircraft reference trajectory optimization

Aircraft reference trajectory is an alternative method to reduce fuel consumption, thus the pollution released to the atmosphere. Fuel consumption reduction is of special importance for two reasons: first, because the aeronautical industry is responsible of 2% of the CO2 released to the atmosphere, and second, because it will reduce the flight cost. The aircraft fuel model was obtained from a numerical performance database which was created and validated by our industrial partner from flight experimental test data. A new methodology using the numerical database was proposed in this thesis to compute the fuel burn for a given trajectory. Weather parameters such as wind and temperature were taken into account as they have an important effect in fuel burn. The open source model used to obtain the weather forecast was provided by Weather Canada. A combination of linear and bi-linear interpolations allowed finding the required weather data. The search space was modelled using different graphs: one graph was used for mapping the different flight phases such as climb, cruise and descent, and another graph was used for mapping the physical space in which the aircraft would perform its flight. The trajectory was optimized in its vertical reference trajectory using the Beam Search algorithm, and a combination of the Beam Search algorithm with a search space reduction technique. The trajectory was optimized simultaneously for the vertical and lateral reference navigation plans while fulfilling a Required Time of Arrival constraint using three different metaheuristic algorithms: the artificial bee’s colony, and the ant colony optimization. Results were validated using the software FlightSIM®, a commercial Flight Management System, an exhaustive search algorithm, and as flown flights obtained from flightaware®. All algorithms were able to reduce the fuel burn, and the flight costs

A Multi-learning Immune Algorithm for Numerical Optimization

The emergence of nature-inspired algorithms (NIA) is a great milestone in the field of computational intelligence community. As one of the NIAs, the artificial immune algorithm (AIS) mimics the principles of the biological immune system, and has exhibited its effectiveness, implicit parallelism, flexibility and applicability when solving various engineering problems. Nevertheless, AIS still suffers from the issues of evolution premature, local minima trapping and slow convergence due to its inherent stochastic search dynamics. Much effort has been made to improve the search performance of AIS from different aspects, such as population diversity maintenance, adaptive parameter control, etc. In this paper, we propose a novel multi-learning operator into the AIS to further enrich the search dynamics of the algorithm. A framework of embedding multiple commonly used mutation operators into the antibody evolution procedure is also established. Four distinct learning operators including baldwinian learning, cauchy mutation, gaussian mutation and lateral mutation are selected to merge together as a multi-learning operator. It can be expected that the multi-learning operator can effectively balance the exploration and exploitation of the search by enriched dynamics. To verify its performance, the proposed algorithm, which is called multi-learning immune algorithm (MLIA), is applied on a number of benchmark functions. Experimental results demonstrate the superiority of the proposed algorithm in terms of convergence speed and solution quality. Copyright © 2015 The Institute of Electronics, Information and Communication Engineers.Embargo Period 6 month