Term
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Definition
| a hydrophobic binding pocket |
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Term
| What extends down from a helix to bind to the Fe group? |
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Definition
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Term
| Myoglobin saturation curve is |
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Definition
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Term
| hemoglobin saturation curve is |
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Definition
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Term
| What state has a low affinity for oxygen? |
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Definition
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Term
| What state has a high affinity for oxygen? |
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Definition
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Term
| Where can Myoglobin be found? |
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Definition
| heart and skeletal muscles |
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Term
| What property of oxygen is overcome by binding to Hb and Mb? |
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Definition
| limited solubility of oxygen |
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Term
| The primary function is to store oxygen in muscle for release during periods of oxygen deprivation |
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Definition
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Term
| Primary function is to carry O2 from lungs to tissues |
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Definition
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Term
| What can Hemoglobin carry? |
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Definition
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Term
| What is the primary secondary structure seen in Hemoglobin and Myoglobin? |
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Definition
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Term
| How many alpha helices are in Mb? |
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Definition
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Term
| The Heme group in Myoglobin is found in a crevice surrounded by? |
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Definition
| non-polar a.a.'s and 2 Histidines |
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Term
| Tell me the location of the two His in Mb? |
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Definition
| proximal F8 and distal E7 |
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Term
| Why is the crevice in Mb mostly non-polar? |
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Definition
| To prevent the oxidation of Fe2+ to Fe3+, which can not bind to O2 |
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Term
| What is the inorganic portion and organic portion of Heme? |
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Definition
inorganic -Fe
organic- porphyrin ring
4-pyrrole groups linked via CH2 bonds
with 8 substituents
-4 methyl groups
-2 vinyl groups
- 2 propionate groups |
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Term
| Fe makes how many coordinated bonds in Heme? |
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Definition
6 total
4- nitrogens of pyyrole rings
1- His93 (F8)
1- empty, O2, CO, and H20 |
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Term
| What is the purpose of distal His64 (E7)? |
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Definition
| protects the distal side chain of Fe; it reduces space forcing O2 to bind at an angle; its main role is to decrease the affinity of Fe for CO |
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Term
| What is Mb called when the 6th coordinated position is empty? |
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Definition
| deoxymyoglobin; charge of Fe is 2+ |
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Term
| What is Mb called when the 6th coordinated position has O2 in it? |
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Definition
| Oxymyoglobin; Fe charge is 2+ |
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Term
| What is Mb called when the 6th coordinated position has H20 in it? |
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Definition
| Ferrimyoglobin; Fe charge is 3+ |
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Term
| What do you need to reduce Ferrimyoglobin or metmyoglobin? |
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Definition
| metmyoglobin reductase in the presence of co-factor NADH and co-enzyme cytochrome b4 |
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Term
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Definition
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Term
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Definition
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Term
| O2 affinity in Hb is dependent on... |
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Definition
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Term
| events at one active site of one subunit can influence events at active sites of other subunits |
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Definition
| Cooperativity- aspect of quaternary protein structure is essential to Hb |
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Term
| In this model of cooperativity for Hb allosteric changes occur in unison |
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Definition
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Term
| In this model of cooperativity for Hb allosteric changes occur sequentially |
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Definition
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Term
| What is the molecular weight of Hb? |
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Definition
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Term
| How many residues in the alpha proteins? |
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Definition
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Term
| How many residues in the beta proteins? |
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Definition
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Term
| What is released when skeletal or cardiac muscles are damages? |
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Definition
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Term
| Mb in the blood is called |
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Definition
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Term
| Is Fe in the plane of the ring when O2 is not bound? |
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Definition
| No it is raised up slightly by His93 (F8) |
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Term
| What happened in Sickle cell anemia? |
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Definition
| Valine replaces glutamate on the Beta 2 chain of Hb, this valine binds into the hydrophobic pocket of Beta-1 subunit of another Hb and this happens for a lot of these creating long fibers |
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Term
| What happens during physical activity? |
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Definition
| When the pH is reduced, certain histidines become protonated, which alters salt linkage formation, and reduces oxygen affinity. This results in a shift of the oxygen-hemoglobin association curve to the right, indicating a stabilization of the tense (deoxy) form of hemoglobin. Under these conditions the hemoglobin is binding protons, and not releasing them. |
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Term
| What increases the proportion of T state? |
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Definition
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Term
| What sits where the B and E helices cross over each other-it is highly conserved because of this? |
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Definition
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Term
| What is directly involved in the binding site? It helps protect the pocket so Fe2+ does not become oxygenated and forces O2 to bind sideways |
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Definition
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Term
| This is also in the heme pocket, it binds directly to Fe2+ |
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Definition
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Term
| At lower pH, the histidines tend to from salt bridges with ________, contributing to the stability of the T-form of hemoglobin in tissues. It forms a salt link with imidazole His146. |
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Definition
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Term
| hydroxyl group forms hydrogen bond with Val98 carbonyl |
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Definition
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Term
| carboxyl group forms a salt link with Lys40 from a-chain |
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Definition
| His146- this is the C terminal a.a., so it uses its primary carboxyl group to form the salt link |
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Term
| What makes HbA have a sigmoidal binding curve? |
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Definition
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Term
| What binds BPG more weakly so it is more attracted to O2? |
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Definition
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Term
| Negative charges on BPG bind to deoxy Hb via electrostatic interactions with basic amino acid residues |
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Definition
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Term
| At physiological pH: BPG has how many (+/-) charges? It interacts with how many (+/-) of which chain of Hb? |
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Definition
BPG-4 neg charges
B-chain of Hb has 6 pos charges |
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Term
| What is a difference between HbF and HbA? |
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Definition
| His143 is substituted by Ser |
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Term
| In HbF, beta chains are replaced by? |
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Definition
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Term
| When going from T to R states... |
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Definition
| movement of helices decreases the size of the cavity for binding BPG (steric hindrance, BPG not happy) |
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Term
| high altitudes increase what in our bodies |
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Definition
| BPG- this will facilitate dumping of O2 into our tissues |
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Term
| This refers to protonating various groups within hemoglobin as the pH drops? |
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Definition
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Term
| T/F There are no covalent bond in the tertiary and quaternary structures of Hb. |
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Definition
| True-only salt bridges, hydrophobic interactions and H-bonds |
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Term
| Is the Bohr effect pertinent to Mb? |
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Definition
| No, it the cooperativity model to work. |
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