Friday, March 29, 2019

Filamentous DNA Phages Single Stranded RNA Phages

Filamentous desoxyribonucleic acid bacteriophages Single Stranded ribonucleic acid Phages mental hospitalBacteriophages atomic number 18 one of the most widely studied organisms than that of bacteria and each other living organism. They argon generally apply in that of molecular biology studies, because of lesser complexity they ar usually preferred all over other organism.A bateriophage is a bacterial para office which hobo incomplete grow or repplicate on its own unless can do so at bottom a given organism.The major supremacy of bacteriophage truly depends upon the genetic element which is usually packed within the mirid. the genetic element can either be a superstar forsake or double run agrounded linear,circular deoxyribonucleic acid /ribonucleic acid.The filamentous bacteriophages are single detached desoxyribonucleic acid phages most 5.5nm in diameter and they usually are present in a ring wish motley. They manhoodeuver the presence of about ten thou sand nucleotide and they usually harbour in Gram negative host. They usually adsorb on the tail exchangeable component called sex fuzz which is responsible for the transmission of plasmids. The major properties of these virus are that it does not harm the host.The other general properties of filamentous desoxyribonucleic acid phages are as followsThey can be grown in extremely high titre because they do not lyse the cells.They are extremely pocket- size in size and they can mainly be studied and used in molecular biology experiments.It is the only virus which has been crystallized for the compend using roentgenogram diffraction and a good model for studying mutations.The fundamental interaction between the host and the virus can be used as a model for studying characteristics property of oncogenic virus.Three filamentous E.coli phages i.e M13,fd, f1 discombobulate been carefully studied and each of them have a vivification roulette wheel similar to that 174.M13 bacteriophag eM13 is a filamentous bacteriophage it has circular ssDNA. It stocks about 6407 nucleotides. It contains major coat protein P8 and it capped with 5 minor protein P9,P6,P3.P3 protein attaches to the tip of the pilus E.coli. They are non-lethal and they form turbid plaques in Ec.oli they bring about reducing in the cell growth cultivate. They are excessively used for geomorphological studies.The phage particles The phage is assembled by that of 50 amino acids protein called p8.It takes about 2700 copies of p8 to fix about the coat 90 nm gigantic.It has been seen that is quite flexible .Other apparent proteins which are usually present P9 mainly comprises about 5 copies.P7 p9 are usually seen in micrographs they are extremely small in size containing about 32-33 amono acids.The other end of the phage particles contain about 5 copies of the surface exposed p3and less exposed accessory protein p6.They form a rounded tip and the p6 is the the final protein to interact with the E.co li host during invasion.Phage life cycleThe filament phage uses the F pilus to infect E.coli with the M 13 tip containing the TolA protein on bacterial pilus. The phage genome is transferred to the cytoplasm of E.coli where the house physician protein convert single rimed DNA genome to a double stranded replicative form(RF).This DNA acts like a template for the expression of phage gene. The help phase mainly involves amplification of the genome p2 it nicks the double strand form of the genome to spring up the replication of strand without which no replication occurs. Host enzymes replicate the(+) strand resulting in more copies of dsDNA.p5 competes with ds DNA formation by sequestering copies of the (+) stranded DNA into a protein/DNA complex designed to pack retrieval phages. Another important protein p10 is important for regulating the number of ds genome in the bacterial host without which no strand an accommodate .Phage maturation requires p4 transmutational restart p11.Mul tiple copies of p4 assemble in outer membrane into a remand barrel shaped structure.A number of p1 and p11 5/6 copies each)assemble inside the inward bacterial membrane.p1 p11 ans p4 together they are responsible for the release of arise phage.REPLICATION IN M13Replication in m13 can be explained as followsViral (+) strand DNA enterscytoplasmComplementary (-) strandis synthesized by bacterial enzymesDNA Gyrase, atype II topoisomerase, acts ondouble-stranded DNAand catalyzes formation ofnegative supercoilsin double-stranded DNAFinal product is parental replicative form (RF) DNAA phage protein, pII, nicks the (+) strand in the RF3-hydroxyl acts as a primer in the creation of new viral strandpII circulizes displaced viral (+) strand DNAPool of progeny double-stranded RF molecules produced minus strand of RF is template of transcriptionmribonucleic acids are translated into the phage proteinsPhage proteins in the cytoplasm are pII, pX, and pV, and they are part of the replication pro cess of DNA. The other phage proteins are synthesized and inserted into the cytoplasmic or outer membranes.pV dimers give impudently synthesized single-stranded DNA and prevent conversion to RF DNARF DNA synthesis continues and amount of pV reaches critical concentrationDNA replication switches to synthesis of single-stranded (+) viral DNApV-DNA structures from about 800nm long and 8nm in diameterpV-DNA complex is substrate in phage manufacture reaction.ResearchSINGLE STRANDED RNA PHAGESSingle stranded RNA are found everywhere E. coli lives in the intestinal tract of man and animals. They can also be found in sewage samples .They are harmless creature in case of humans.RNA phages are tailless, icosahedron like that of 174 and it mainly involves E. coli phages f2,R17,MS-2 Q. The RNA is a linear single stranded molecule having about 3600 nucleotides it contains 3 genes encoding a coat protein an attachment protein (A) and a RNA replicase. The RNA molecule acts both like a template and also like an mRNA so they do not possess a DNA polymerase and the regulation occurs at the translational level. They have large break down size and they form huge crystalline arrays within each bacterium. mobile phone lysis usually takes place at a time ranging from 30-60 minutes later on infection.Virus structure Virions contain about 180 copies of the coat protein lay in a T=3 icosahedral shell that encloses THE RNA. alloleviviruses contain about 15 copies of the read through protein.the encapsidated RNA is resistant to ribonucleinase treatment.The damaged virion are exposed to RNAase activity.The structures have been resolved by x-ray diffraction methodsLife cycle of RNA PHAGEENTRY Upon entry the ribosome they usually attach to the CP gene which is the centremost gene of the RNA molecule.TRANSLATION The stem and closed circuit structures in RNA block the ribosomal binding sites of the A and the Rep proteins. The translation of the CP gene opens the binding site of the R ep proteins .Both proteins are made but the increasing amounts of the CP proteins bind to the rep site and block translation of the rep gene. About 2 x 10 copies are needed as structural components whereas replicase is needed only in catalytic amounts.Replication of the phage RNAThe Qhas a tetramer consisting of one Rep molecule with about deuce-ace proteins-EF-Ts EF-Tutranslation factors needed for the placement of charged TrnaMOLECULESSynthesis of A protein The binding site for the A protein is never available on the free(+)strand. The replication begins at the 3teerminus close to the A gene. After synthesis of the (+) strand begind there is a brief period when the protein A gets translated. The A number is maintained and it is pertain to the number of the (+) strand .it is believed that the A protein bring about the interaction of the RNA with the CP moleculesPARTICLE ASSEMBLY THE CP PROTEIN MOLE CULES spontaneously aggregate around the newly synthesized (+) strand and form an icosahedral shell.Cell lysis Once about 10000 phages are formed the cell undergoes lysis and no lytic enzymes are left place ,the mechanism still remains un cognize.The Q phageIt is an RNA virus impact E.coli.Contains a positive sense single strand RNA.It is one of the smallest known viruses measuring about 24 nm in diameter.Its icosahedral capsid consists of about 180 copies of the same protein. The strands acts like that of an mRNA and it also acts like a template for the replication of a complimentary strand.REFERENCESFilamentous bacterial Viruses(BACTERIOLOGICAL REVIEWS JUNE 1969 pg 177-209.ASM PRESSTHE BACTERIOPHAGES 2ND ,BY CALENDER EDITION OXFORD PRESSMOLECULAR biological science BY FREIFIELDERFROM THE WEB

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