Single-stranded binding protein
Single-stranded binding proteins (not to be confused with the E. coli protein, Single-strand DNA-binding protein, SSB) are a class of proteins that have been identified in both viruses and organisms from bacteria to humans. The only organisms known to lack them are Thermoproteales, a group of extremophile archaea, where they have been displaced by the protein ThermoDBP (Thermoproteales-specific DNA Binding Protein). While many phage and viral single stranded binding proteins function as monomers and eukaryotes encode heterotrimeric RPA (Replication Protein A), the best characterized SSB is that from the bacteria E. coli which, like most bacterial single stranded binding proteins exists as a tetramer.
Single stranded binding proteins prevent premature annealing, to protect the single-stranded DNA from being digested by nucleases, and to remove secondary structure from the DNA to allow other enzymes to function effectively upon it.
Single Stranded DNA-binding protein(icp8) from Herpes simplex virus-1
In ICP8, the Herpes simplex virus (HSV-1) single stranded DNA (ssDNA)-binding protein (SSB), The head consists of the eight alpha helices. The front side of the neck region consists of a five-stranded beta-sheet and two alpha helices whereas the back side is a three-stranded beta-sheet The shoulder part of the N-terminal domain contains an alpha-helical and beta-sheet region. The Herpes simplex virus (HSV-1) single stranded DNA (ssDNA)-binding protein (SSB), ICP8, is a nuclear protein that, along other replication proteins is required for viral DNA replication during lytic infection.
Six herpes virus-group-common genes encode proteins that likely constitute the replication fork machinery, including a two-subunit DNA polymerase, a helicas-primase complex and a single-stranded DNA-binding protein. The Human herpesvirus 1 (HHV-1) single-strand DNA-binding protein ICP8 is a 128kDa zinc metalloprotein. Photoaffinity labeling has shown that the region encompassing residues 368-902 contains the single-strand DNA-binding site of ICP8. The HHHV-1 UL5, UL8, and UL52 genes encode an essential heterotrimeric DNA helicase-primase that is responsible for concomitant DNA unwinding and primer synthesis at the viral DNA replication fork. ICP8 may stimulate DNA unwinding and enable bypass of cisplatin damaged DNA by recruiting the helicase-primase to the DNA.
Crystal structure of PriB- a primosomal DNA replication protein of Escherichia coli
In molecular biology, SSB protein domains in bacteria are important maintaining DNA metabolism, more specifically DNA replication, repair and recombination. It has a structure of three beta-strands to a single six-stranded beta-sheet to form a dimer.
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- Single-Stranded DNA Binding Proteins at the US National Library of Medicine Medical Subject Headings (MeSH)
- SSB in PFAM