Term
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Definition
| contains only amino acids |
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Term
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Definition
| contains amino acids + non-amino acid component (prosthetic group) |
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Term
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Definition
| conjugated protein minus prosthetic group |
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Term
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Definition
| oxygen carrying protein in red blood cells |
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Term
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Definition
| oxygen binding protein in muscle |
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Term
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Definition
| globin protein (composed of AA) |
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Term
| For Hb and Mb, prosthetic group is |
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Definition
| heme group (protoporphyrin composed of 4 pyrrole rings) |
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Term
| Physiological role of Myoglobin: |
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Definition
a) found in heart and skeletal muscle
b) serves as oxygen reservoir |
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Term
| Protein structure of Myoglobin |
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Definition
1) Compact, globular protein
2) 75% alpha helix content
3) 4 helices are terminated by Pro residues (Pro=helix breaker)
4) is so compact that there is no room for water in its interior |
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Term
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Definition
| name given to the protein structure of Mb and Hb where the 8 helices create a pocket and wrap around the porphyrin ring |
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Term
| Heme pocket of globin protein |
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Definition
- serves to keep iron in 2+ oxidation state
- this insures that reversible oxygen binding occurs |
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Term
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Definition
- when iron is in 2+ oxidation state
- ferrohemoglobin or ferromyoglobin is formed and can reversibly bind oxygen |
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Term
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Definition
- when iron is in 3+ oxidation state
- ferrihemoglobin or ferrimyoglobin is formed and does not bind |
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Term
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Definition
| also called methemoglobin |
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Term
| Picket-fence iron porphyrin |
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Definition
| - heme with synthetic carbon chains attached - synthetic chains create an artificial pocket on the exposed side of 2+ ferrous ion - can mimic oxygen binding of Mb and Hb |
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Term
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Definition
α₁β₁ dimer and β₂α₂
- the two subunits of each dimer are tightly associated, but the two dimers are more loosely associated and slide by each other |
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Term
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Definition
- oxyHb
- relaxed form
- more compact
- fewer salt bridges b/w mobile dimers
- β subunits closer together
- no cavity in tetramer
- 33 Å b/w β chains |
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Term
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Definition
- deoxyHb
- taut form
- more extended
- more salt bridges b/w mobile dimers
- β subunits further apart
- 40 Å b/w β chains |
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Term
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Definition
| binding of first ligand makes it easier to bind the second ligand etc. |
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Term
| Oxygen dissociation curve |
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Definition
| plot of % Saturation of Hb or Mb on y-axis vs. partial pressure of oxygen (pO₂) on x-axis |
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Term
| Compare O₂ dissociation curves for Hb and Mb |
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Definition
1) Mb has higher O₂ affinity (Mb is half-saturated at 1 mm Hg, Hb is half-saturated at 26 mm Hg)
2) Mb dissociation curve is hyperbolic, Hb dissociation curve is sigmoidal |
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Term
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Definition
a diagnostic plot used to evaluate the extent of cooperativity which exists in a biological system
- plot log (y/1-y) vs. log pO₂
- represents a linear transformation |
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Term
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Definition
slope (n) of the line at midpoint of binding
- n=1, no cooperativity (binding sites are independent)
- n > 1, positive cooperativity (sites are interdependent)
- n increases with degree of cooperativity (max. value of n equals the # of binding sites that are interdependent) |
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Term
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Definition
| some molecule (other than O₂) that binds to a Hb allosteric site and alters Hb O₂ binding |
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Term
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Definition
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Term
| 2 categories of allosteric protein sites |
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Definition
1) Ligand binding site
2) Allosteric site |
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Term
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Definition
heme group where O₂ binds
- "work site" |
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Term
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Definition
another site on the protein where an allosteric effector binds and changes the affinity of the protein for its ligand
- "regulatory site" |
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Term
| 3 Allosteric Effectors of Hb |
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Definition
| H+, CO₂, and 2,3-bisphophoglycerate (BPG) |
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Term
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Definition
| lowering pH reduces the affinity of Hb for O₂ |
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Term
| Lowering the pH does what to the Hb O₂ dissociation curve? |
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Definition
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Term
| H+ bonding does what to the Hb O₂ dissociation curve? |
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Definition
| make the curve more sigmoidal |
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Term
| 3 functional groups of "T" with greater H+ affinity |
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Definition
| β-142 histidine, α-122 histidine, & α-NH₂ group of α chain |
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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
| Sequential model for allosteric interactions |
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Definition
subunits change conformation one at a time
- Koshland proposed |
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Term
| Concerted model for allosteric interactions |
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Definition
subunits all change conformation together
- monod, wyman, and changeux proposed |
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Term
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Definition
| effects due to allosteric interaction b/w identical ligands, as exemplified by the cooperative binding of O₂ to hemoglobin |
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Term
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Definition
| effects due to allosteric interactions b/w different ligands, as exemplified by the decrease in O₂ binding elicited by H+, C0₂, and BPG |
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