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The F factor was the first plasmid to be discovered. Unlike other plasmids, F factor is constitutive for transfer proteins due to a mutation in the gene finO. [4] The F plasmid belongs to F-like plasmids, a class of conjugative plasmids that control sexual functions of bacteria with a fertility inhibition (Fin) system. [5]
The fertility plasmid or F-plasmid was discovered by Esther Lederberg and encodes information for the biosynthesis of sex pilus to aid in bacterial conjugation. Conjugation involves using the sex pilus to form a bridge between two bacteria cells; this bridge allows the F+ cell to transfer a single-stranded copy of the plasmid so that both cells contain a copy of the plasmid.
For example, the F plasmid, which is the origin of BACs (bacterial artificial chromosomes) is a single copy plasmid with a partitioning system encoded in an operon right next to the plasmid origin. The partitioning system interacts with the septation apparatus to ensure that each daughter receives a copy of the plasmid.
Genes on the F plasmid specifies the proteins of the F pilus, which includes the F-pilin protein that serves as the viral receptor. MS2 attaches to the F-pilin on the side of the pilus using its single maturation protein. Once the viral RNA has entered the cell, it begins to function as a messenger RNA for the production of phage proteins. The ...
A bacterial artificial chromosome (BAC) is a DNA construct, based on a functional fertility plasmid (or F-plasmid), used for transforming and cloning in bacteria, usually E. coli. [ 1 ] [ 2 ] [ 3 ] F-plasmids play a crucial role because they contain partition genes that promote the even distribution of plasmids after bacterial cell division.
The majority of the R-RTF (Resistance Transfer Factor) molecules are found in the resistance plasmid, which can be conceptualized as a circular piece of DNA with a length of 80 to 95 kb. [citation needed] This plasmid shares many genes with the F factor and is largely homologous to it. [15]
When conjugation is initiated by a signal the relaxase enzyme creates a nick in one of the strands of the conjugative plasmid at the oriT. Relaxase may work alone or in a complex of over a dozen proteins known collectively as a relaxosome. In the F-plasmid system the relaxase enzyme is called TraI and the relaxosome consists of TraI, TraY, TraM ...
Later structures of the Mob relaxases TrwC from plasmid R388 [5] and TraI from the F-plasmid [6] confirmed that the Mob and Rep classes are evolutionarily related to one another through circular permutation. This means that they share a general fold, but the amino-terminal sequence of one is homologous to the C-terminus of the other, and vice ...