User:Olsen-in-HD/sandbox/FtsK
FtsK
[edit]Structure
[edit]FtsK is a transmembrane protein composed of three domains: FtsKN, FtsKL, and FtsKC.[1] The FtsKN domain is embedded in the cellular membrane by four transmembrane α-helices.[2] The FtsKL domain extends from the membrane into the cytoplasm.[2] This linking domain varies in length across many bacteria.[2] Found at the cytoplasmic end of the linker domain, the FtsKC segment of the protein is responsible for enabling the activity of the Xer recombination system upon the formation of a chromosome dimer.[2]
Additionally, the FtsKC domain is composed of three subdomains: α, β, and γ.[1] The α and β subunits aggregate to form a hexamer that possesses the ability to translocate DNA through ATP hydrolysis.[1][2] The ATP hydrolysis sites are found on the β subunits of the hexamer.[2] The γ domain is responsible for the control of the hexamer.[2] It mediates the attachment of the hexamer to double-stranded DNA, controls the directionality of the translocase, and initiates chromosome dimer segregation.[2]
Mechanism of Action
[edit]The dif site
[edit]The dif site is found on at the intersection between the monomers of the chromosome dimer.[2] It corresponds to where chromosomal replication ceased and is also the site of Xer mediated segregation.[1] Translocation of the FtsKC hexamer stops when it reaches the location of the Xer recombinase complex that is associated with the dif site.[1]
Binding Site
[edit]Guanosine rich areas of DNA, which are found at the ends of the dif region, are the sites of translocation initiation.[2] These sites are referred to as KOPS motifs.[2] Upon binding a KOPS motif, the FtsK hexamer forms and proceeds towards the dif region.[1][2] Movement toward the dif region is facilitated by the polarity of the KOPS motif.[2]
Translocation
[edit]There are three proposed mechanisms of DNA translocation: the rotary inchworm, the staircase, and the revolution mechanism.[2] The rotary inchworm mechanism involves two points of contact between DNA and the FtsKC hexamer.[2] These points of contact correspond to a α and a β subunit.[2] A conformational change in the α subunit can cause the DNA to shift.[2] This shift is followed by a conformational change in the β subunit (which also causes the DNA to move). The repeated conformational changes lead to the translocation of DNA.[2]
Conversely, the staircase mechanism see the α and β subunits of the hexamer interacting with the double-stranded DNA in a sequential manner.[2] Conformational changes in each subunit cause movement in the spatial position of the DNA strand.[2] Additionally, the revolution mechanism entails the passing of DNA through a channel formed by the hexameric FtsKC domain[2]. In general, the chromosome dimer is translocated so that the site of resolution is near the divisome and so one copy of the genetic material ends up in each daughter cell.[2]
Recombinase (Xer D) activation
[edit]The recombination apparatus is made up of four monomers, two being Xer D and two being Xer C, that belong to a family of tyrosine recombinases.[1] The interaction of Xer D and the γ subunit of FtsKC results in the activation of the recombinase.[1] Contact between Xer D and the γ subunit is facilitated by the translocation of DNA.[2] Specifically, translocation stops when the FtsKc hexamer reaches the dif site.[2]
Role in cell division
[edit]FtsK has been shown to be a part of the divisisome of bacteria.[2] FtsKN is thought to both stabilize the septum and aid in the recruitment of other proteins to the site of cell division.[2] Studies have shown that part of the FtsKN domain (which is in the periplasm) is involved in the construction of the cell wall.[2]
References
[edit]- ^ a b c d e f g h Brenner's encyclopedia of genetics. Maloy, Stanley R.,, Hughes, Kelly, (Second edition ed.). San Diego, CA. ISBN 9780080961569. OCLC 836404630.
{{cite book}}:|edition=has extra text (help)CS1 maint: extra punctuation (link) CS1 maint: others (link) - ^ a b c d e f g h i j k l m n o p q r s t u v w x y z aa Crozat, Estelle; Rousseau, Philippe; Fournes, Florian; Cornet, François (2014). "The FtsK Family of DNA Translocases Finds the Ends of Circles". Journal of Molecular Microbiology and Biotechnology. 24 (5–6): 396–408. doi:10.1159/000369213. ISSN 1464-1801.