Download Sos response in E. coli

SOS response in E. coli
By
Dan Wilson
SOS response in E. coli
 The bacterium is exposed to something that
damages its DNA.
For example: Radiation or some type of
mutagen that will damage the bacterial DNA.
 After damage occurs lesions will appear
damaging sections of the DNA.
SOS response in E. coli
• If the damage is too great then normal repair
mechanism may not be able to repair the
damage.
• If there is not a lot of lesions then
sometimes normal replication methods can
repair the DNA
• DNA sequence is lost where there are lesions
SOS response in E. coli
• Damaged DNA
• Replicated DNA with top
strand
• DNA replicated with
damaged strand.
SOS response in E. coli
• Two key proteins involved in the response are
LexA and RecA.
• LexA is a repressor protein under normal
conditions and inhibit the SOS response
• RecA when the DNA is damaged this protein
inactivates the LexA protein cleaving it and
this triggers the SOS response.
SOS response in E. coli
• If the lesions are more widespread then the
SOS response is used.
• During DNA replication when DNA polymerase
gets to the damaged spot it basically give its
best guess as to what the missing DNA
sequence should be.
SOS response in E. coli
• This system is far from perfect and mutations
can occur.
• Mutations….
• Antibiotic resistance.
Works Cited
Campbell, M., & Farrell, S. (2012). Biochemistry. Belmont California:
Brooks/Cole. Page 271
Friedman, N., Vardi, S., Ronen, M., Alon, U., & Stavans, J. (2005). Precise
temporal modulation in the response of the SOS DNA repair network in
individual bacteria. Plos Biology, 3(7), e238 :
http://search.ebscohost.com/login.aspx?direct=true&db=cmedm&AN=15
954802&site=eds-live
Michel, B. (2005). After 30 years of study, the bacterial sos response still
surprises us. Plos Biology, Retrieved from
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1174825/