Hemoglobin Flashcards
What four subunits is HbA made of?
two alpha subunits
two beta subunits
What four subunits is HbA2 made of?
two alpha
two delta
What four subunits is HbF composed of?
two alpha
two gamma
What amino acid substitution is present in HbF? What can this new amino acid bind?
histidine to serine
23BPG
What chromosome are the alpha globins located?
16
What chromosome are the beta globins located?
11
HS-40 corresponds to what globin gene?
alpha
LCR corresponds to what globin chain?
beta
What is the amino acid substitution during HbS?
glutamate to valine
What drug is used to manage HbS? Why is this drug used?
Hydroxyurea
increases levels of HbF
What amino acid residue is present during HbC? What is thought to happen to HbC?
glutamic acid to lysine
crystallization
What amino acid substitution is present during HbS?
glutamate to valine
How many genes are there for α-globin? What chromosome?
four
16
In a person with severe (three gene deletion) α-thalassemia, what form of hemoglobin will form? What globin isotypes make this up?
Hb Barts
four gamma chains
When fetal Hb production winds down, what form of Hb will a person with severe α-thalassemia produce? What globin chain isotypes make this up?
HbH
four beta chains
Why are Hb Barts and HbH poor oxygen transporters?
too high of O2 affinity
What amino acid substitution is present during HbE? Where?
glutamate to lysine
southeast asia
What is the only α-thalassemia that can be caused by a point mutation? What is produced?
Hb constant spring
excessively long α2 chain
What type of recombination takes places in Hb Lepore?
fusion of beta and delta
At a pH of 8.6, will HbA be positively or negatively charged?
negatively
What amino acid of hemoglobin can protons bind? What other amino acid will this charged histidine now bind?
histidine
aspartate
What is formed when CO2 binds Hb?
carbamates
At what position is the amino acid substitution in HbS? What chain?
position 6
beta chain
Which hemoglobinopathy has the same position and chain error as HbS?
HbC
What position in the mutation in HbE? What chain? What happens to this globin?
26
beta chain
inefficient synthesis
During HbLepore, what part of the mRNA contains delta globin? Beta globin?
delta = N-ter
beta = C-ter
What is the function of HS-40 and LCR?
tissue specific expression of Hb
What do HbS homozygotes have? Heterozygotes?
homozygotes = disease
heterozygotes = trait
If four α-globin genes are deleted, what are the two isotypes of α-globin that can predominate?
Gower
Portland
What is the error during Hb Constant Spring?
stop codon is changed to a glutamine residue
Does Hb Constant Spring behave like a α+ or an α0 thalassemia?
α+
What are the three Hb’s produced in the early embryo?
Gower 1, Gower 2 and Portland
What does oxidized Fe3+ form?
hemichrome
In what population is HbC confined?
West Africans
What type of problems can accumulate in a patient with HbSC?
ocular
Why can HbS and HbA be separated on an electrophoresis?
HbS is slightly more negative
What restriction endonuclease is used for PCR HbS vs. HbA?
Mst II
Other than polymerizing, what does the valine in HbS accomplish?
block O2 binding site on β-chain
What is the amino acid substitution in Hb Helsinki? Where? What does this result in?
Lys to Met
2,3-BPG binding site
increased O2 affinity
What is the amino acid substitution in Hb kansas? What does this result in?
Asn to Thr
decreased oxygen affinity
What are the two hemoglobinopathies that readily form methemoglobin?
boston and hyde park
What is the common error for almost all α-thalassemias? Due to what?
deletion
homologous recombination
