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DNA primase is an RNAP enzyme involved in the replication of DNA.

Primase catalyzes the synthesis of a short RNA segment (called a primer) complementary to a ssDNA template. Primase is of key importance in DNA replication because no known DNA polymerases can initiate the synthesis of a DNA strand without an initial RNA or DNA primer (for temporary DNA elongation).

Contents

Function

In bacteria, primase binds to the DNA helicase forming a complex called the primosome. Primase is activated by DNA helicase where it then synthesizes a short RNA primer approximately 11 ±1 nucleotides long, to which new nucleotides can be added by DNA polymerase.

The RNA segments are first elongated by DNA polymerase and then synthesized by primase.[1] Then the DNA polymerase forms a protein complex with two primase subunits to form the alpha DNA Polymerase primase complex. Primase is one of the most error prone and slow polymerase. [2] Primases in organisms such as E coli, synthesize around 2000 to 3000 nucleotides at the rate of one nucleotide per second.[3] Primase also acts as a halting mechanism to prevent the leading strand from outpacing the lagging strand by halting the progression of the replication fork. [4] The rate determining step in primase is when the first phosphodiester bond is formed with the ssDNA. [5] The crystal structure of primase in E. coli with core that contained the DnaG protein was determined in 2000. [6] The DnaG and primase complex is cashew shaped and contains three subdomains. [7] The central subdomain forms a toprim fold which is made of a mixture five beta sheets and six alpha helices. [8] The toprim fold is used for binding regulators and metals. The primase uses a phosphotrasfer domain for the transfer coordination of metals, which makes it distinct from other polymerases. [9] The side subunits contain a NH2 and COOH terminal made of made of alpha helixes and beta sheets. [10] The NH2 terminal interacts with a zinc binding domain and COOH-terminal region which interacts with DnaB-ID. [11] The replications mechanisms differ between different between bacteria and viruses where the primase covalently link to helicase in viruses such as the T7 bacterialphage. [12] In viruses such as herpes simple virus (HSV-1), primase can form complexes with helicase.[13] The primase-helicase complex is used to unwind dsDNA and synthesizes the lagging strand using RNA primers.[14] The majority of primers synthesized by primase are two to three nucleotides long.[15]

Types

External links

References

  1. ^ Griep, Mark A. (1995). "Primase Structure and Function". Indian Journal of Biochemistry & Biophysics 32.  
  2. ^ Griep, Mark A. (1995). "Primase Structure and Function". Indian Journal of Biochemistry & Biophysics 32.  
  3. ^ Keck, James L. , and Daniel D. Roche, A. Simon Lynch, James M. Berger. (2000). "Structure of the RNA Polymerase Domain of E. coli Primase". Science 282.  
  4. ^ Lee, Jong-Bong , and Richard K. Hite, Samir M. Hamdan, e.t. al. (2006). "DNA primase acts as a molecular brake in DNA replication". Nature 436.  
  5. ^ Griep, Mark A. (1995). "Primase Structure and Function". Indian Journal of Biochemistry & Biophysics 32.  
  6. ^ Keck, James L. , and Daniel D. Roche, A. Simon Lynch, James M. Berger. (2000). "Structure of the RNA Polymerase Domain of E. coli Primase". Science 282.  
  7. ^ Keck, James L. , and Daniel D. Roche, A. Simon Lynch, James M. Berger. (2000). "Structure of the RNA Polymerase Domain of E. coli Primase". Science 282.  
  8. ^ Keck, James L. , and Daniel D. Roche, A. Simon Lynch, James M. Berger. (2000). "Structure of the RNA Polymerase Domain of E. coli Primase". Science 282.  
  9. ^ Keck, James L. , and Daniel D. Roche, A. Simon Lynch, James M. Berger. (2000). "Structure of the RNA Polymerase Domain of E. coli Primase". Science 282.  
  10. ^ Keck, James L. , and Daniel D. Roche, A. Simon Lynch, James M. Berger. (2000). "Structure of the RNA Polymerase Domain of E. coli Primase". Science 282.  
  11. ^ Keck, James L. , and Daniel D. Roche, A. Simon Lynch, James M. Berger. (2000). "Structure of the RNA Polymerase Domain of E. coli Primase". Science 282.  
  12. ^ Lee, Jong-Bong , and Richard K. Hite, Samir M. Hamdan, e.t. al. (2006). "DNA primase acts as a molecular brake in DNA replication". Nature 436.  
  13. ^ Cavanaugh, Nisha A., and Robert D. Kuchta (2009). "Initiation of New DNA Strands by the Herpes Simplex Virus-1 Primase-Helicase Complex and Either Herpes DNA Polymerase or Human DNA Polymerase alpha.". J. Biol. Chem 284.  
  14. ^ Cavanaugh, Nisha A., and Robert D. Kuchta (2009). "Initiation of New DNA Strands by the Herpes Simplex Virus-1 Primase-Helicase Complex and Either Herpes DNA Polymerase or Human DNA Polymerase alpha.". J. Biol. Chem 284.  
  15. ^ Cavanaugh, Nisha A., and Robert D. Kuchta (2009). "Initiation of New DNA Strands by the Herpes Simplex Virus-1 Primase-Helicase Complex and Either Herpes DNA Polymerase or Human DNA Polymerase alpha.". J. Biol. Chem 284.  
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