Exam 1- Myoglobin & Hemoglobin Flashcards
Globins
A superfamily of proteins containing the globin fold which is composed of 6-8 alpha helices arranged in a characteristic HEME-enclosing structure
Which part of the globin fold binds heme?
HisF8 and HisE7
Describe the main differences between myoglobin & hemoglobin
- Myoglobin is present in muscle, Hb in the blood
- Mb is a monomer, Hb is a tetramer of alpha/beta globulin chains
Function of heme
To bind and unwind O2. Only works with Fe2+ center
Describe heme structure
Mostly hydrophobic, planar. Carboxyl in aqueous phase.
Has 6 positions. First 4 associated with n of tetrapyrrole ring. Last 2 are perpendicular bonds that interact with HisE7 and F8
Heme/O2 interactions
Heme with Fe2+ binds O2
Heme with Fe3+ will created superoxide ion
Heme(Fe3+)- metmyoglobin or methemoglobin
P50
The PO2 at which half of the binding sites are occupied
P50 for Hb vs Mb
Hb ~ 26 torr
Mb ~ 3 torr
Hill equation
Log(y/1-y) = n (log pO2 - log P50)
Where,
Y= fractional saturation. y: bound. (1-y): not bound
n= Hill coefficient
nmax = # subunits
No cooperativity: n=1
Positive cooperativity: n>1
Negative cooperativity: n <1
Mb: n=1
Hb: n=2.8
Right shift causes
Improved oxygen delivery
Right shift is induced by
H+ increase (pH decrease)
CO2 increase
2,3BPG increase
T increase
2,3BPG binds to _____
Deoxy Hb between beta chains
When O2 decreases, 23BPG binds Hb, allowing for more O2 delivery
Hemoglobin-Nitrite interactions
Hb Fe 2+ can bind NO. Carry and extend life of NO
This rxn releases a metHb or metMb - Hb(Fe3+)
MetHb/MetMb reductase reduces Fe3+ to Fe2+ regenerating normal Hb and Mb
Hb during development
Alpha and gamma Hb before birth
Alpha and beta Hb after birth
Sickle cell mutation in beta gene
In which gene does sickle cell anemia occur
Beta gene of Hb
