Update septu.md

Modifying Septu for #205 (closed)

content/3.defense-systems/septu.md

@@ -21,13 +21,13 @@ relevantAbstracts:
 # Septu
 
 ## Description
-The Septu defense system was discovered in 2018 in *Bacillus* :ref{doi=10.1126/science.aar4120}. The name of the system is related to Septu (or Sopdu) the ancient egypt god of the sky and of eastern border regions.
+The Septu defense system was discovered in 2018 in *Bacillus* :ref{doi=10.1126/science.aar4120}. The name of the system is related to Septu (or Sopdu) the ancient Egypt god of the sky and eastern border regions.
 
-The Septu defense systems is composed of two protein PtuA and PtuB: PtuA encoding for an ATPase (AAA15/AAA21) and PtuB with HNH endonuclease domain.
+The Septu defense system is composed of two proteins PtuA and PtuB: PtuA encoding for an ATPase (AAA15/AAA21) and PtuB with an HNH endonuclease domain.
 
-After the discovery of Septu, two studies discovered separatly another form of Septu :ref{doi=10.1093/nar/gkab883,10.1016/j.cell.2020.09.065}. This new subtype encode a thrid protein with a reverse transcriptase domain. This system is either reffer as Septu Type II :ref{doi=10.1093/nar/gkab883} or as [Retron](/defense-systems/retron) subtype RT-I-A :ref{doi=10.1016/j.cell.2020.09.065,10.1016/j.cell.2020.09.065}.
+After the discovery of Septu, two studies discovered separately another form of Septu :ref{doi=10.1093/nar/gkab883,10.1016/j.cell.2020.09.065}. This new subtype encodes a third protein with a reverse transcriptase domain. This system is either referred as Septu Type II :ref{doi=10.1093/nar/gkab883} or as [Retron](/defense-systems/retron) subtype RT-I-A :ref{doi=10.1016/j.cell.2020.09.065,10.1016/j.cell.2020.09.065}.
 
-The Septu defense system is part of large category of system that encode the AAA15/21 ABC ATPase :ref{doi=10.1111/mmi.15074}.
+The Septu defense system is part of a large category of systems that encodes the AAA15/21 ABC ATPase :ref{doi=10.1111/mmi.15074}.
 
 ## Molecular mechanism
 The structure of the PtuAB complex shows a stoichiometry of 6:2 (A:B) :ref{doi=10.1038/s41594-023-01172-8}.
@@ -36,7 +36,7 @@ The CTD terminal domains of the external PtuA bind to the PtuB endonuclease.
 
 The PtuB is an HNH endonuclease like  Cas9 :ref{doi=10.1016/j.cell.2014.02.001} that cleaves the phage DNA :ref{doi=10.1038/s41594-023-01172-8}.
 
-Interestingly, the ATPase domain of PtuA has no ATPase activity. However, the experimentaly determined structure shows that 4 ATPs bind inside the PtuA hexamer :ref{doi=10.1038/s41594-023-01172-8}. The authors then show that the endonuclease activity of PtuAB is down-regulated by ATP in a concentration dependant manner.
+Interestingly, the ATPase domain of PtuA has no ATPase activity. However, the experimentally determined structure shows that 4 ATPs bind inside the PtuA hexamer :ref{doi=10.1038/s41594-023-01172-8}. The authors then show that the endonuclease activity of PtuAB is down-regulated by ATP in a concentration-dependent manner.
 
 Authors :ref{doi=10.1038/s41594-023-01172-8} hypothesize that the PtuAB complex is inactive in noninfected cells by the physiological concentration of ATP. During phage infection, the pool of ATP can be depleted leading to the activation of the PtuAB complex and the phage DNA cleavage by PtuB HNH endonuclease.