Vibrio Cholerae Cytolysin (VCC) Membrane Pore Formation

Vibrio Cholerae Cytolysin (VCC) Membrane Pore Formation Vibrio cholerae cytolysin (VCC) is a potent membrane pore forming protein toxin secreted by many pathogenic strain of the V.cholerae. In its membrane pore-formation mode of action, VCC belongs to the family of the ÃŽ ² barrel pore-forming toxin (ÃŽ ²-PFTs) proteins. VCC is secreted by the pathogenic bacteria V.cholerae in the form of water-soluble, monomeric, inactive precursor form of the protein, known as Pro-VCC. Proteolytic deletion of the N-terminal Pro-domain from this inactive precursor molecule generates the active, mature form of the VCC toxin. VCC induces colloid-osmotic lysis of the target eukaryotic by generating the transmembrane heptameric ÃŽ ² barrel channels/pores. The high-resolution molecular structural information is available for the water-soluble monomeric Pro-VCC form as well as for the transmembrane heptameric pore structure of the VCC. Structural analysis of the water-soluble monomeric form and the transmembrane structure suggest that the VCC follows the overa ll pattern of the archetypical ÃŽ ²-PFTs mechanism of pore-formation. However, the distinct intermediate steps leading the generation of the funcational membrane pore formation by VCC have only been characterized to a limited extent. Consistent with the generalized ÃŽ ²-PFTs mode of action, the membrane pore formation mechanism of the VCC is recommended to follow three different steps: interaction of the VCC monomeric unit towards the target cell membrane; formation of the metastable, transient prepore oligomeric intermediates on the cell membrane; and finally conversion of the prepore oligomeric assembly into the functional transmembrane oligomeric b barrel channels. Previous research work on the members of ÃŽ ²-PFTs including VCC suggest that the generation of the functional transmembrane oligomeric pore structure comprises the membrane insertion of the pore-forming stem region from each of the toxin protomer towards formation of the transmembrane ÃŽ ² barrel portions of the toxin. However, it has not been examine experimentally, in particular in the case of VCC toxin, whether the membrane insertion of the stem region could occur in the membrane-associate monomeric state of the toxin before the prepore oligomer generation or whether the prepore oligomer generation precedes the membrane insertion of the stem region of the VCC toxin. Even in the case of generalized ÃŽ ²-PFTs membrane pore-formation mechanism, such sequence of pore formation events has not been established precisely. Previous studies demonstrated that the engineered ÃŽ ²-PFTs (for example, VCC and staphylococcal LukF) not able to inserting their pore-forming stem region into the membrane lipid bilayer of the target cell membrane. Such protein variants, having their stem loop in a closed structure through the engineered disulfide linkage, are remaining trapped in their nonfunctional prepore oligomeric state. However form this observation it not clear whether the membrane oligomreization is absolutely necessary to trigger the membrane insertion or whether membrane insertion could be initiated before the prepore generation. Such perception can only be investigate by trapping the b-PFTs toxin molecule in its membrane-bound monom eric form without allowing the generation of the transmembrane oligomeric structures. In this order, a direct correlation between the membrane oligomerization and the membrane insertion has been demonstrated in Staphylococcal à ¯Ã‚ Ã‚ ¡ toxin, an archetypical member of the ÃŽ ²-PFTs family. Staphylococcal à ¯Ã‚ Ã‚ ¡ toxin containing a single point mutation has been shown to displayed defective membrane oligomerization of the membrane-bound protein and blocking the membrane insertion of the pore-forming stem loop of the toxin. This investigation suggests that, in case of Staphylococcal à ¯Ã‚ Ã‚ ¡ toxin, the membrane insertion event of the toxin depend critically on the prior membrane oligomrization step of the toxin. A similar pore-forming mechanism has been reported in the case of perfringolysin O, a prominent member of the subclass of the cholesterol-dependent cytolysin (CDC) under ÃŽ ²-PFTs family. Interestingly, streptolysin O, another prominent member in the cholesterol-de pendent cytolysin type ÃŽ ²-PFTs, follows a different mechanism of membrane pore formation that may have involve distinct sequence of events. In the membrane pore formation mechanism of streptolysin O, it has been proposed that the progressive assembly of the membrane-inserted monomeric unit of the toxin may act towards the formation of the transmembrane oligomeric pore structures of different pore sizes. A similar membrane oligomeric assembly has also been reported on another cholesterol-dependent cytolysin (CDC) class of ÃŽ ²-PFTs, pneumolysin. Thus, it emerge that the ÃŽ ²-PFTs member may not necessarily follow a common generalized procedure for the membrane pore formation mechanism of the toxin. It is, therefore, important to examine the sequence of the membrane oligomreization and insertion events for each particular member of the ÃŽ ²-PFTs family to elucidate the molecular mechanistic details of their membrane pore-formation action of the toxin. Many previous studies explored the molecular mechanism(s) of the membrane oligomerization process involved with the membrane pore formation action of the member of the ÃŽ ²-PFTs family including VCC. It is generally proposed that the association of the ÃŽ ²-PFTs protein monomer with the membrane component of the target host cells work as the triggering step to initiate the following events resulting towards membrane olgiomerization, membrane insertion, and functional transmembrane ÃŽ ² barrel pore formation. In particular, lipid components of the membrane like cholesterol have been extensively involved in the regulating of membrane pore formation process. In the mode of action of VCC, the presence of cholesterol in the target membrane lipid bilayer has been reported to be an imperative requirement for the efficient oligomerization and functional membrane pore formation by the protein. Cholesterol appears to regulate the membrane pore-formation of the toxin by physically binding with the protein molecule and not by modulating the physicochemical environment of the target host cell membrane. The molecular mechanism of the membrane oligomerization in VCC has been explored only to a limited extent. In particular, the membrane interaction mechanism of the monomeric units of the VCC toxin, which probably acting to regulate the membrane oligomerization process of the VCC toxin, has not been explored so far. Structure analysis of the VCC oligomeric highlights the major interprotomer interactions between the neighboring monomer units. The most significant interactions are observed between the amino acid residues within the membrane pore forming stem loop of the toxin. More importantly, blocking the stem loop in its prestem configuration has been to abrogate the functional transmembrane oligomeric pore formation (SDS-stable oligomeric assembly) without any effect on the generation of the prepore oligomeric species (SDS-labile oligomers). It has been reported that, even i n the physically absence of the stem loop, a truncated variant of VCC can generate prepore oligomeric assembly on the membrane. These observations precisely suggest that the interprotomer interactions involved in formation of the functional transmembrane oligomeric pore assembly without playing any critical role in initiating the membrane oligomerization event of the membrane-bound protein molecules. Therefore, it appears that the additional molecular interaction between the monomer of the toxin might be playing the significant role in inducing the functional membrane oligomerization of the VCC toxin. In this part of study, to explore the details of the molecular mechanism of the membrane oligomerization process of the VCC toxin, we have mapped the key amino acid residue in the VCC molecular structure that are crucial to trigger the membrane oligomerization of the membrane-associate monomeric toxin molecules. Mutation of such key amino acid residues abrogates the membrane oligomerization step, trap the toxin in its membrane-bound monomeric state, and does not allow membrane insertion of the pore-forming stem loop form the VCC monomers. Our study, dissect the membrane interaction step from the following membrane oligomerization and insertion steps of VCC as a prototype in the b-PFTs family, This study also conclusively established that the membrane insertion critically required the functional oligomerization of the membrane-associate VCC toxin monomers on the target cell membrane.

Why One Should Not Steal

Someone would say stealing is only right when you are poor, homeless, or to help your family. There are many times when people have said â€Å"we needed to steal even though we did not want to, because we had to survive. † In my opinion, no matter what the circumstances are, stealing anything, from anyone, is not morally right, is unjust, causes consequences, and most importantly, defies, breaks, and sometimes completely diminishes, trust. Although I did not intentionally steal from my parents, this essay will be about why stealing money from parents is wrong.First of all, stealing things is not morally or ethically, the right thing to do. At a young age, people learn that taking things from other people without their permission is not going to be accepted as good behaviour. It is important to know that if something isn’t yours, you do not have a right to it. I’m pretty sure even in the bible it says; â€Å"thou shall not steal. † If you know something is going to be frowned upon if done, or that you would be frowned upon, upon participating in something, you simply should not partake in that action.Another reason stealing should not be performed, is because it is unjust. Just like Antoine Lavoisier's Law of Conservation of Mass, to gain something physical from one person, means that person must have lost something. Stealing money from someone means that the amount you took is the amount they lost, and they have to make up for that loss somehow. This is not fair, because the person earned that money themselves, and should not have to work extra, to accommodate more than just them. The effort they are making for the money is not equal to the effort the thief is making, which is unjust.Thirdly, people should refrain from robbing others, is because what comes with crime or bad behavior, is consequences. Stealing is obviously against the law. If caught doing it, it could cause you to have that on your record and this could hinder you fro m getting a job, etc. Not to mention, in the end, it is your loss, because you would get fined, or have to pay off the value of what you had taken. On a less lawful note, your parents could find out, and this could bring about many repercussions, of their choice.If that doesn’t scare you, you are of another species. Lastly, and most importantly, stealing destroys almost all trust you had with the person you stole from. Robbing things can leave someone, such as my parents, to feel utterly betrayed. They think they have a good relationship with you, and then when you take something from them without their permission, it can make them re-evaluate the bond they have with you. Stealing makes people feel vulnerable and sad, like you used them, and don’t care about their feelings, values, beliefs or thoughts.This can seriously affect what they (and other people) think of you, and you never know, you may need them at some point and they won’t be there to help you. This is because they will remember what you did to them, and think twice before doing something nice to/for you. Clearly, it is not worth it to steal anything, from anyone because it will not affect you positively in the end. I have learned my lesson, and will never take money if I am not one hundred percent sure it is mine. My sincere apologies for my actions, and I will pay you back every penny of it.

Analysis Of Robert Frost s Birches - 3014 Words

The most misinterpreted element in Robert Frost poetry is his use of nature in a symbolic way. Frost is not describing the inner workings of nature as we see it all around us, but about exploring human psychology. For example, Frost uses Homely farmers, rural scenes, landscapes, and the natural world to epitomize a psychological struggle with an everyday experience that is often met with courage, will, and purpose; contextually, using Frost’s own life and personal psychology. Frost’s attitude in his poetry is honest, accepting, and stoical, nature is just used as a background. Frost usually begins his poems by delineate an observation of something in nature, then moves on toward a connection with some human concern or situation. He uses the natural world as symbolism in his poetry then suggests bigger, deeper, more complex ideas. In Robert Frost’s poetry he is not purely writing about nature, rather he is using nature as a tool to compose ideas relating to h uman nature. In Robert Frost’s poem â€Å"Birches† he uses nature as imagery to convey his disdain for the pressures of social life. Frost does not specify which social burden he is referring too, but we can piece together parts of this poem and derive at his true meaning. The language Frost uses in â€Å"Birches† tell us there is a burden such as, †¦ â€Å"Often you must have seen them†¦Loaded with ice†¦ Such heaps of broken glass to sweep away†¦ They are dragged to the withered bracken by the load, †¦though once they are bowed†¦ SoShow MoreRelatedEssay on Hardships in Birches by Robert Frost1013 Words   |  5 PagesHardships in Birches by Robert Frost In any life, one must endure hardship to enjoy the good times. According to Robert Frost, the author of Birches, enduring lifes hardships can be made easier by finding a sane balance between ones imagination and reality. The poem is divided into four parts: an introduction, a scientific analysis of the bending of birch trees, an imaginatively false analysis of the phenomenon involving a New England farm boy, and a reflective wish Frost makes, wantingRead MoreThe Poetry Of Robert Frost3137 Words   |  13 Pagesexamine the poetry of Robert Frost for references to themes of nature, religion, and humanity and how they relate to each other. This exercise will be prefaced with a brief introduction to the man and his life as a segue to better understanding Frost’s verse. The unexpected but unavoidable aim of this composition will be to realize that Frost’s body of work is almost too sophisticated to comprehend, his manipulation of language so elusive that each reader may believe Frost is speaking only to themRead MoreRobert Frost : A New England Poet3698 Words   |  15 PagesRobert Lee Frost Known for being a New England poet Robert Frost was born in San Francisco, California on March 26th, 1874. Born to a New England father William Prescott Frost Jr. and a Scottish mother Isabelle Moodie who moved to the west coast from Pennsylvania after marriage (Bailey). Both his parents were teachers and poets themselves, but his father later became a journalist with the San Francisco Evening Bulletin (Bailey). Frost spent 12 years of his life growing up in San Francisco, untilRead MoreANALIZ TEXT INTERPRETATION AND ANALYSIS28843 Words   |  116 Pagesï » ¿TEXT INTERPRETATION AND ANALYSIS The purpose of Text Interpretation and Analysis is a literary and linguistic commentary in which the reader explains what the text reveals under close examination. Any literary work is unique. It is created by the author in accordance with his vision and is permeated with his idea of the world. The reader’s interpretation is also highly individual and depends to a great extent on his knowledge and personal experience. That’s why one cannot lay down a fixed â€Å"model†

Lilies of the Field - 3461 Words

Lilies of The Field is a book written by William Barrett. Mr. Ralph Nelson, a producer, was introduced to this book by his agent Fred Ingles. Ralph Nelson was so intrigued by this story that he wanted to put it on film. Finally after much negotiation it was brought to the silver screen in 1963 by Mr. Ralph Nelson with a very low budget. With determination and tenacity Mr. Nelson achieved his dream. The entire film was shot in fourteen days! Incredibly, the picture was nominated for four Academy Awards, including Best Picture. Additionally, Lilies of the Field achieved motion picture history as Sidney Poitier was awarded the Best Actor Oscar, marking the first time in history an Academy Award was awarded to a black man. Choosing this†¦show more content†¦Throughout all of the negotiations, there is an underlying spiritual undertone which drives the negotiation on both sides. There are ethical issues and spiritual issues which motivate the outcome of each negotiated battle. They both have needs and wants, and it becomes a battle which often may be directed by the notion of God himself. During the first negotiated moment the process standard is clear, Mother Maria is the dominate negotiator, she is strong, forthright and determined. She easily overpowers Mr. â€Å"Schmidt† as she refers to him, into staying and fixing their roof. Mr. Smith gives in and accepts her offer because he is in need of gas money. His thoughts and needs are simple; he wants gas money so that he can be on his way. Mr. Smith considered her deal as a win-win for himself. He realizes that his needs will be considered therefore, he assumes he will benefit from this agreement. Mother Maria, on the other hand, needs M r. Smith to stay on longer she wants him to build a church chapel. Mr. Smith agreed to fix the roof for monetary compensation. Mother Maria agreed that he would be compensated after the work is done. Unfortunately, Mother Maria withheld information; she didn’t have any money to pay him, and she knew that. Ethics played a large role in my analysis of Mother Marias tactics. Of course, she may have thought that she was doing the work of God; therefore, ethics was a non-issue. However in negotiations ethic is very important.Show MoreRelatedA Negotiation Analysis of Lilies of the Field3998 Words   |  16 Pagesï » ¿Lilies of the Field: A Negotiation Analysis Introduction This paper will give a negotiation analysis of the film Lilies of the Field and show how it is, in effect, a negotiation of power between two strong-willed individuals, Homer Smith and Mother Maria, both of whom get (by way of compromise) what they want in the end. The synopsis of Ralph Nelsons 1963 film adaptation of Lilies of the Field is simple: an African-American itinerant worker named Homer Smith stops at a poor farm in theRead MoreDada Has a Flashback667 Words   |  3 Pages Turns out that the girl is Patsy, her new best friend. The bus reaches Avenger FIeld, and the girls get lined up and their names are called. Soon they go to their bunk house and share their stories on why they wanted to be a WASP. The next day they start their training. 10-12 The girls meet their instructor, Martin. They get parachutes and are ready to fly. The plane they are about to fly is the PT-19A. Lily goes first and falls out of the plane. Next, Ida goes up into the air. Ida figuresRead MoreSpecific Roles of Characters Depicted in Sue Monk Kidds The Secret Life of Bees1073 Words   |  5 Pagesevery duty. Lily and Zach are the field bees, August is a nurse bee, and the Lady of Chains is the Queen bee. Field bees have great navigational skills tireless hearts. They go out to the fields everyday and gather the nectar and pollen from all the flowers and return it to their hive. Lily and Zach both have great navigational skills and tireless hearts. Not to mention they go out every day to help gather all the honey from the fields just like the bees gather nectar and pollen. Lily traveled allRead MoreAnalysis Of Snow Flower And The Secret Fan1421 Words   |  6 Pageswritten by Lisa See in 2005, is a coming of age story accounting the life of Lily, a girl born in Puwei, China, in 1823. Puwei was a poor town, but not poor enough to force women to perform field work. Lily received a laotong relationship with Snow Flower, which is a relationship of eternal kindship between two girls. This relationship allowed Lily to raise in station and marry into a richer family. The story focused on Lily and Snow Flower’s relationship with each other and finding their place inRead MoreThe Se cret Life Of Bees Directed By Gina Prince Bythewood890 Words   |  4 Pagesmuch of Sue Monk Kidd’s writing was based in the antebellum south. In the movie, Lily the main character runs away from her father and stays with August Boatwright, June Boatwright, and May Boatwright, the women who nurtured her mother, to find out the truth about her mom. Race serves as a major social barrier that Lily has to overcome when she lives in the Boatwright sisters African American household. Even though Lily does not mean to come off as racist or socially privileged, her background instillsRead MoreSnow Flower And The Secret Fan Analysis1469 Words   |  6 Pagestraits. It is from these traits that the characters can either help themselves or destroy themselves. The two girls, Lily and Snow Flower, are the foils in the book. Both girls are to live together in a jibe. Nevertheless, as time goes on, their relationship becomes strained. Their difference in following orders creates this stra in. Whereas Snow Flower wants to go against orders, Lily does not, developing unthinkable circumstances such as death and destruction. (Look over this paragraph all together)Read MoreState Symbols of Tamilnadu1416 Words   |  6 PagesBinomial name Chalcophaps indica FLOWER:( GLORIOSA LILY) Gloriosa is a genus of ten species in the plant family Colchicaceae, and include the formerly recognised genus Littonia. They are native in tropical and southern Africa to Asia, and naturalised in Australia and the Pacific as well as being widely cultivated.The most common English names are flame lily, fire lily, gloriosa lily, glory lily, superb lily, climbing lily, and creeping lily. They are tender, tuberous rooted deciduous perennialsRead MoreIn American Novelist Harper Lee’S To Kill A Mockingbird,1555 Words   |  7 Pagesaloud to her kitten about the weather, asserting, â€Å"I wonder if the snow loves the trees and fields, that it kisses them so gently?’† (156). When Alice talks to her kitten, as if it is a real person, she shows that she cannot distinguish the difference between imagination and reality. This quote is also an example of personification because Alice states how she believes the snow loves to â€Å"kiss the trees and fields† because of the way it falls. She is still developing mentally as a child and is in theRead MoreRay Bradbury s Fahrenheit 451 Government Control And Fear1488 Words   |  6 PagesMontag. Consider the lilies of the field. ‘Denham’s Dentifrice.’ They toil not- ‘Denham’s-’ Consider the lilies of the field, shut up, shut up. ‘Dentifrice!’ He tore the book open and flicked the pages and felt of them as if he were blind, he picked at the shape of the individual letters, not blinking. ‘Denham’s. Spelled: D-E-N-’ They toil not, neither do they†¦ A fierce whisper of hot sand through empty sieve. ‘Denham’s does it!’ Consider the lilies, the lilies, the lilies†¦ ‘Denham’s dental detergent