Hemoglobin 1.2 Flashcards
What are the two globin chains in the alpha form?
zeta and alpha
What chromosome has gene for alpha globin chains
16
What are the genes on the alpha chain
How many alleles responsible for alpha chain?
zeta alpha alpha (on each chromosome)
4 total alleles/loci (two from each chromosome)
What globin chains belong to Beta forms
epsilon G-gamma G-alpha delta Beta
What chromosome has gene for beta chain
Chromsome #11
What is the gene cluster that encodes the alpha chain of human Hb
zeta, psi-zeta-; psi-alpha2; psi-alpha1; alpha2, alpha1, theta
What is the gene cluster that encodes the beta chain of human Hb
G-Gamma, A-gamma, psi beta, delta, beta
How many exons and introns per gene
3 exons
2 introns
Hb A1
alpha2, beta2
Hb A2
Alpha2, delta2
HbF
alpha2, gamma2
Hb Gower 1
zeta2, epsilon2
Hb Gower 2
alpah2, epsilon2
Hb Portland
zeta2, gamma2
Which chains are present at britha nd quickly decline up to 6months
Zeta and Epsiolon
which globin chain is at its peak at 6 months
beta chains
which rises after first tirimester then declines after birth?
gamma chain
which chain increses after first tirmester and is steady in adult life
alpha
which globin chain appears only after birth and is seen in HbA2
delta
which chain decreases at birth? Increases?
beta chain increaess
gamma chain decreases
What chromosome is the gene for Mb ?
22
How many identities (identical) between BETA and DELTA
138
Identities between Beta and Gamma
108
Between Beta and Alpha
65
What is the location of the proximal HIS in Hb
HIS F8
directly binds to HEME
what is location of distal HIS in Hb. What is it’s function?
HIS E7
This HIS is displaced by Oxygen when O2 binds to Hb
how many hemes are there/tetramer
4
What percent is given to tissues with normal Hb (%) from lungs to tissue
66% unloaded
How much oxygen is unloaded from lungs to tissue with myoglobin
7%
How much oxygen would beunloaded if there were no cooperativity in Hb
38%
Does the PO2 of arterial blood vary with exercise? Does venous blood?
Arterial- no
Venous- pO2 willd rop with exercise
21% aoxygen released at reast
45% oxygen released with exercise
How much oxygen unloaded with lowered pH to 7.2
77% (shift right)
How much Oxygen released with pH 7.2 and 40 torr CO2
88%
what percent shift to right of O2 curve is due to lowered pH (or higher H+)
75%
What percent of shift of O2 curve to right due to carbamylation of N-terminal alpha-amino group
25%
What percent is due to modification
…13% of transported CO2 is carried on Hb
Does H+ bind stronger to oxygenated or deoxygenated Hb. Why? Mechanism
Deoxygenated.
Affinity for proton is higher b/c deoxyHb is a weaker acid, has higher pH
0.5 proton taken up upon deoxygeantion
Three gorups are ore negative environment in Deoxy Hb
- His 122a
- His 146b
- alpha amino
What is the net charge of 2,3, BPG?
4-5 net negative charge at physio pH
How do you get 2,3,BPG
it is a byproduct of glycolysis (no TCA in RBC)
How many binding sites of BPG on tetramer
one!
What conditions lead to elevation of 2,3, BPG (2_
- Hypoxia (increased elevation)
2. Anemia
How is BPG lost in bloo?
lost in blood stored in citrate-gucose
How is BPG maintained?
with inosine via ribose –> pentose shunt –> more BPG
How do you get BPG
mutatse from 1,3 BPG – >2,3 BPG–> hyrolysis to 3 PG
What 3 positively charged groups does BPG interact with on the beta chain
Lys 82
His 143
His 2
Does HbF have higher or lower affinity for O2 than maternal Hb (HbA)? Why?
Fetal red cells have HIGHER oxygena ffinity
b/c HbF:
- Binds BPG less strongly than HBA
- has higher oxygen affinity with rbc (BPG)
Helsp with transfer of oxygen from maternal to fetal
What are regulatros of HbO2 (5) ; all make the curve shift right –> lowers oxygen affinity
{H+}
CO2
BPG
Cl-
Temp increase
How does the quarternary structure change in oxygenation of Hb
alpha1, beta1 shifts 15 degrees, with a translation of 0.8 Anxgroms going form DEOXY (T state) to OXY (R state)
How does the quarternary structure change in oxygenation of Hb
alpha1, beta1 shifts 15 degrees, with a translation of 0.8 Anxgroms going form DEOXY (T state) to OXY (R state)
What is broken during conformational change from deoxy to oxy Hb
noncovalent salt bonded (ionic bonds) between alpha nd beta chains are disrupted upon oxygenatino
Lys C5 = H-bonded to beta group of C terminus, asp. FG1
What happens to Fe atom on oxygenation?
Fe atom moves INTO plane of heme on oxygenation b/c its diameter becomes SMALLER.
His F8 (proximal) is pulled along with Fe2+ and becomes less tilted
What are the tetrameric interactions id DeoxyHb(T)
- all inersubunit salt bridges intact
2. one BPG molecule bound between Beta chains
What are tetrameric changes in OXy Hb (R state)
sal bridges beween subunits are borken
BPG is expelled
Tertiary and Quarternary structures change
Describe Deoxy Hb (T state)
- Extra bonds form last 2 residues of the beta chain
Fe out of plane toward helix F
Tyr displaces SH groups form pocket between helixes F adn H; forms a bond with Val FG 5
What causes shft to right?
Increase in red cell 2,3, BPG
What causes incrase in red cell 2,3,BPG
1.High altitutde adaptation
2. pulmonary hypoxemia
3. cardiac right to left shunt
4. severe anemia, decrese in red cell mass
5. congestive heart failture
6 decompensated hepatic cirrhosis
7. thyrotoxicosis
8. Hyperphosphatemia (ATP alos increased)
What causes shift to left
Decrease in red cell 2,3 BPG
what causes decrease in 2,3, BPG
septic shock severe acidosis following transfusions of store blood Hypophophatemia panhypopitutitiarism neonatal respiratory distress syndrome
functonally abnormal Hb variatnts
Methemoglobinemia
CO intoxiation
What causes dissociation curve to shift to LEFT
- Methemoglobinemia
2. Carbon Monoxide Intoxication
What is the preferential conformation for CO binding to isolated Iron Porphyrin? What is CO:O2 affinity ratio in this confirmation?
Linear mode of binding
CO:O2= 200:1
What prevents CO from binding linearly (forces it to bind bent,so affinity not as strong)
Distal HIS
What protects Hb(Fe2+) from oxidizing to Fe3+?
Distal/proximal HIS
What type of oxidants oxidize Fe2+ –> Fe3+?
Sulfonamide
What is required to convert MetHb 3+ –> Fe2+
MetHb Reductase
what is missing in Familial Mehemoglobinemia? What is the mutation
MeHb Reductase
Tyr substituted for the proximal his- iron gets oxidiezed to ferric form
Also true for try subsittution for distal His (E7)
What is presentation of trace CO in air
5% HbCO
Impaired vision
0.02% of CO in air
20% HbCO
headache, nausea
0.1 CO in air
40-60% HbCO
death (red color
What is normal % HmM
1.7%
Cyanosis due to HbM
10%
Genetic HbM
15-30%
headeache, weakness, breathlessness due to HbM
> 35%
Death due to HbM
70%
How many babies are born with SCD annually in Afical and will die befor age of 5 fromanemia and infection?
200,000
How many Afro-Americans are heterozygous % for HbAS sickcle cell trait
7-10%
How many are homozygous -afflicate for HbSS , SCD
0.4% 50-72,000
What is the mutation that causes Deoxy HbS to be insoluble and sickle?
There is a Glu–> Val @ Beta 6
from (-) –> (0) so now H-phobic patches/interactions of Val with Ph–> Polymerization
What does the electrophoresis show for HbS vs HbA
HbA travels further up towards + charge (b/c GLu is negative)
while HbS is lower and does not travel as far on the gel
What does the PEPTIDE MAP of HbA and HbS show?
that there is a difference in one spo of the peptide –> you can sequence this to find position where mutation occured!
2D chroatogorpahy/eletorphoresis
Why is there pain the in periphery with SCD
HbS –> sickled cells polymerize and are less flexible, they can’t squeeze through
Esp in spleen
What are the treatments for SCD
hyroxyurea, 5-azactydine (increases HbF)
BM transplant
Gene therapy
Inhibition of HbF silencing protein (BC11A)–HbF will help create more HbF
What is B^0
2 Beta alleles missing
Cooley Anemia B
Thalassemia Major
What is B+
1 allele missing
clinical effect seen later
What is HPFH1
Hereditary Persistant Fetal Hemoglobinemia
Delete Beta alleles
Affets Gamma gene upstream –> turns on Gamma gene–> get HbF!! inc affinity of O2 –> can funciton b/c there is similar allosteric features
Gamma has lower affinity for BPG in RBC
What causess Lepore
No A2 (no delta)
what are non-deletion forms of Beta thalassemia mutations
usually single base changes in, or upsream of beta gene
What are deletion forms?
different sizes; B0, HPFH, multiple, hybride
HbH
B4- acts like monomer
Hb Bart’s (Hyrops Fetalis)
Gamma4-
What form of Fe usually comes from food
Fe3+, low pH, ascrobic acid in stomach
What form of iorn is needed to pass through membranes
Ferrous form Fe2+
what does Ferroxoxidase do?
oxidize Fe2+ –> 3+ in plasma ,so iron can bind to Transferrin
What is the role of Transferrin
to transport Fe3+ to tissuess when low in Fe , needed for Hb
What can Iron overload lead to? What is the mutation?
hereditary hemochromatosis (primary = genetic)
H41D mutation in HFE, alpha-MHC-I, related preotine that binds trasferrin receptor
What is seconardy Hemochromatosis
usually caused by transfusions
undiagnosed, untreated iron overlaod, regardless of its orgin lead to diabetes, arthritis, depression, impotetece, liver-gall bladder disease, complete liver failure, hear attack and cancer
what is wrong with too much iron?
Causes hemosiderin to form and ferric ion promotes oxidation of other cellular constituents
Inc Fe –> Lipid peroxidation
inc apoferritin syntehsis
increases lysosome lability leads to release of acid hyrolases
damage cells
inc fe upteake by paranchymal cells
