RecG protein: Difference between revisions
From Proteopedia
Jump to navigationJump to search
No edit summary |
No edit summary |
||
| Line 1: | Line 1: | ||
'''RecG''' [[Image:RecG.jpg | thumb ]] | '''RecG''' [[Image:RecG.jpg | thumb ]] | ||
The RecG protein of Escherichia coli is a Superfamily 2 (SF2) branched-DNA-specific helicase which promotes rescue of damaged replication forks by catalysing their unwinding and conversion to Holliday junctions. A single RecG monomer unwinds two DNA duplexes; the leading strand duplex and the lagging strand duplex and then reanneal the parental and the newly synthetized strands. This mechanism of repair is ATP-dependent and does not require DNA double strand break. RecG works synergistically with the RuvABC repair system<ref>Singleton, M. R., Scaife, S. & Wigley, D. B. Structural analysis of DNA replication fork reversal by RecG. Cell 107, 79–89 (2001)</ref>,<ref>Rudolph, C. J., Upton, A. L., Briggs, G. S. & Lloyd, R. G. Is RecG a general guardian of the bacterial genome? DNA Repair 9, 210–223 (2010)</ref>. | The RecG protein of Escherichia coli is a Superfamily 2 (SF2) branched-DNA-specific helicase which promotes rescue of damaged replication forks by catalysing their unwinding and conversion to Holliday junctions. A single RecG monomer unwinds two DNA duplexes; the leading strand duplex and the lagging strand duplex and then reanneal the parental and the newly synthetized strands. This mechanism of repair is ATP-dependent and does not require DNA double strand break. RecG works synergistically with the RuvABC repair system<ref name="structure">Singleton, M. R., Scaife, S. & Wigley, D. B. Structural analysis of DNA replication fork reversal by RecG. Cell 107, 79–89 (2001)</ref>,<ref>Rudolph, C. J., Upton, A. L., Briggs, G. S. & Lloyd, R. G. Is RecG a general guardian of the bacterial genome? DNA Repair 9, 210–223 (2010)</ref>. | ||
'''SUPERFAMILY 2 HELICASES''' [[Image:Tileshop.fcgi-2.jpeg | thumb ]] | '''SUPERFAMILY 2 HELICASES''' [[Image:Tileshop.fcgi-2.jpeg | thumb ]] | ||
| Line 18: | Line 18: | ||
Domain 1 is at the N terminus and is about a half of the protein. It contains a long α helix in the center of the domain. This helix provides a rigid structural foundation upon which the rest of the domain is folded. There are two common structural motifs in Domain 1. Residues 21–99 form an antiparallel four helix bundle, preceded by an additional α helix. The second one is a greek key motif (residues 154–252) that is conserved in all RecG sequences. This motif is the binding site of the protein to the DNA. | Domain 1 is at the N terminus and is about a half of the protein. It contains a long α helix in the center of the domain. This helix provides a rigid structural foundation upon which the rest of the domain is folded. There are two common structural motifs in Domain 1. Residues 21–99 form an antiparallel four helix bundle, preceded by an additional α helix. The second one is a greek key motif (residues 154–252) that is conserved in all RecG sequences. This motif is the binding site of the protein to the DNA. | ||
The C-terminal domains: Domains 2 and 3 contain the characteristic motifs that identify RecG as an SF2 helicase. This part of the protein is structurally homologous with other SF2 helicases. ATP binds in the cleft between these domains and induces change in their relative orientation. | The C-terminal domains: Domains 2 and 3 contain the characteristic motifs that identify RecG as an SF2 helicase. This part of the protein is structurally homologous with other SF2 helicases. ATP binds in the cleft between these domains and induces change in their relative orientation. | ||
Domain’s 3 last 50 residues are forming a hook that wraps around the extended α helix of the Domain 1. This interaction provides a link between Domains 1 and 3 that is likely to be affected by nucleotide binding<ref | Domain’s 3 last 50 residues are forming a hook that wraps around the extended α helix of the Domain 1. This interaction provides a link between Domains 1 and 3 that is likely to be affected by nucleotide binding<ref name="structure" />. | ||
'''INTERACTIONS WITH DNA''' [[Image:Phe.jpg | thumb ]] | '''INTERACTIONS WITH DNA''' [[Image:Phe.jpg | thumb ]] | ||
Domain 1 of RecG contacts with DNA at the junction itself, indicating the specificity of the interaction with stalled replication forks. The junction is hold by the greek key motif on one side and an extended β hairpin (residues 259–266) on another. The template strands interact with the protein grooves that are too small to accommodate DNA duplex, resulting in simultaneous split of the leading and the lagging strands. The breaking of the leading strand and the lagging strand duplexes is stabilized by the aromatic ring of Phe 204 and Tyr 208 of the protein, respectively. This mimicks base stacking of a duplex DNA structure. One of the DNA bases doesn’t contact with RecG, serving as a transient state to facilitate flipping between the duplexes during junction migration. | Domain 1 of RecG contacts with DNA at the junction itself, indicating the specificity of the interaction with stalled replication forks. The junction is hold by the greek key motif on one side and an extended β hairpin (residues 259–266) on another. The template strands interact with the protein grooves that are too small to accommodate DNA duplex, resulting in simultaneous split of the leading and the lagging strands. The breaking of the leading strand and the lagging strand duplexes is stabilized by the aromatic ring of Phe 204 and Tyr 208 of the protein, respectively. This mimicks base stacking of a duplex DNA structure. One of the DNA bases doesn’t contact with RecG, serving as a transient state to facilitate flipping between the duplexes during junction migration. | ||
Additionally, the phosphodiester backbones of the duplex arms of the junction are interacting with Domain 1 and 3 of RecG. The interaction allows the formation of either a B-form (DNA) or an A-form duplex (DNA/RNA), what explains why RecG can unwind Holliday junctions (DNA) as well as R-loops (RNA)<ref | Additionally, the phosphodiester backbones of the duplex arms of the junction are interacting with Domain 1 and 3 of RecG. The interaction allows the formation of either a B-form (DNA) or an A-form duplex (DNA/RNA), what explains why RecG can unwind Holliday junctions (DNA) as well as R-loops (RNA)<ref name="structure" />. | ||
'''FUNCTION''' [[Image:Manganon2.jpg | thumb ]] | '''FUNCTION''' [[Image:Manganon2.jpg | thumb ]] | ||
RecG is an enzyme with helicase, translocase and ATPase activity. It binds to a stalled replication fork and converts it into a holliday junction, which can be resolved later by RuvC. | RecG is an enzyme with helicase, translocase and ATPase activity. It binds to a stalled replication fork and converts it into a holliday junction, which can be resolved later by RuvC. | ||
RecG binds initially to the junction with the arms of the fork located at domain 1 of the protein. The orphan base pairs are stabilized by aromatic interactions with the protein. In order to unwind both arms simultaneously, the protein drags the junction across the wedge domain (residues 154–252). Due to steric interference only the template strands on the leading and lagging arms would be able to pass through the grooves on either side of the wedge domain. Therefore, the newly synthetized strands are stripped off the template, but their proximity allows association of these complementary strands to form a four-way junction. This translocation is driven by a repetitive opening and closing of the cleft between Domains 2 and 3 as ATP binds and hydrolyzes, allowing the protein alternately to bind and release the template duplex region, thereby walking along the DNA<ref | RecG binds initially to the junction with the arms of the fork located at domain 1 of the protein. The orphan base pairs are stabilized by aromatic interactions with the protein. In order to unwind both arms simultaneously, the protein drags the junction across the wedge domain (residues 154–252). Due to steric interference only the template strands on the leading and lagging arms would be able to pass through the grooves on either side of the wedge domain. Therefore, the newly synthetized strands are stripped off the template, but their proximity allows association of these complementary strands to form a four-way junction. This translocation is driven by a repetitive opening and closing of the cleft between Domains 2 and 3 as ATP binds and hydrolyzes, allowing the protein alternately to bind and release the template duplex region, thereby walking along the DNA<ref name="structure" />. | ||
'''RELEVANCE''' | '''RELEVANCE''' | ||
