Transcript Siderophores - Bryn Mawr College

Did you know there’s a war going on in your
body, right now?
It’s all about getting and hoarding Iron.
A Siderophore
“iron carrier”
Iron(III) Siderophore
ready for transport
It’s an arms race between
the mammalian immune
system and bacteria in the
search for iron:
enterobactin
transferrin
a) enterobactin removes
iron from transferrin
b) siderocalin intercepts
the ferric complex of
enterobactin
siderocalin
c) bacteria produce
alternative siderophores
such as salmochelin.
salmochelin
Anthrax siderophores
http://www.berkeley.edu/news/media/releases/2006/11/30_siderophore.shtml
“Bacterial-Host Iron Wars”
BERKELEY – University of California, Berkeley
Bacteria need iron to grow.
• In iron-poor microenvironments, biosynthetic genes to make,
secrete, and retrieve siderophores
• Siderophores scavenge ferric iron from the environment.
Mammalian hosts fight back
• They sequester iron in serum via serum albumin and
siderocalin.
• virulent bacteria counterattack by an unusual enzymatic Cglycosylation of the enterobactin scaffold, generating
salmochelins (first detected in virulent salmonella)
• bulky glucosyl moiety prevents sequestration of this tailored
siderophore by siderocalin, allowing retrieval of the iron-loaded
form by the bacteria.
Anthrax bacteria require two siderophores working by two
different mechanisms.
• Siderocalin, the human immune protein, binds the anthrax
bacillibactin siderophore and effectively sidelines it.
• a second "stealth" iron scavenger, petrobactin, to get
around the human defense against the first scavenger.
Petrobactin is not bound by siderocalin.
siderocalin
Fe-enterobactin
Why do we need all that Fe?
Hemes in Hemoglobin
and Cytochromes