Basic Resp physio doubt plz help 2,3BPG

[sadaca]

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Hey guys, Just read this in part of explanation of a resp physio on UW.
"2,3BPG only bind to DEOXYHB"
Is that because it has less affinity for oxygen so more oxygen goes to tissues??

Just want to clarify,
Thanks alot

 

[Nephronlearner]

2,3BPG binding to Hb regulates the amount of oxygen that Hb can bind. It binds to a 'pocket' formed by 2 beta chains in the centre of the Hb as this place is positively charged (histidine, probably?). This leads to 'stiffening' of the structure (ionic bonds) -> taut conformation -> reduces oxygen binding.
The reduced affinity of 2,3BPG-Hb for oxygen makes it easier to provide oxygen to tissues.
2,3BPG has much lower affinity for R conformation (oxyHb) because the 'pocket' doesn't exist in R conformation.
T-to-R transition requires breaking of bonds between 2,3BPG and Hb.

 

[sadaca]

@Nephronlearner - Hey again, Thanks alot! IT makes alot of sense. And yep just checked UWORLD, it binds to Histidine.
Going off of this, for HBF , it says it binds to serine instead of Histidine, therefore low affinity for 2,3BPG. I understand that, that is why HBF has high affinty for O2 and less goes to blood.

UW also says "HbF needs to bind 02 strongly than Adult Hb b/c it must obtain 02 from mothers adults Hb in placenta" Do you get what that means? I thought it binds strongly so it doesn't need mothers 02.

Thanks alot friend

 

[Nephronlearner]

@Nephronlearner - Hey again, Thanks alot! IT makes alot of sense. And yep just checked UWORLD, it binds to Histidine.
Going off of this, for HBF , it says it binds to serine instead of Histidine, therefore low affinity for 2,3BPG. I understand that, that is why HBF has high affinty for O2 and less goes to blood.

UW also says "HbF needs to bind 02 strongly than Adult Hb b/c it must obtain 02 from mothers adults Hb in placenta" Do you get what that means? I thought it binds strongly so it doesn't need mothers 02.

Thanks alot friend

It needs to have higher affinity for oxygen so as to extract oxygen from mother's adult Hb (foetus gets oxygen from mother's blood -> foetal Hb steals oxygen from adult Hb -> needs higher affinity for that).
That happens because the gamma chains of HbF have less positive charge (serine instead of histidine) thereby binding of 2,3BPG is reduced -> affinity for oxygen is higher.

 

[sadaca]

Okay great that makes sense. I used to get confused b/c I thought high affinity for O2 here meant it doesn't let go of o2, so how does it extract from mom's? But I get it now

Thanks buddy!