Protein Structure and Fonction Flashcards
What do Proteins do?
They are involved in movement, catalysis, communication and transport
How do proteins do all of their tasks
The essence of a protein’s function is in its interaction with other molecules
What force stabilizes the shape of the protein
Non-covalent interactions
What is a Zwitterion
A neutral (overall) ion with a positive and negative charges. It occurs when the pH is between ~2-9.5
What is pKa?
Reflection of the strength of an acid
What happens when we are at a pH > pKa
Then the [A-] > [HA]
What happens when we are at a pH < pKa
Then the [A-] < [HA]
What happens to the charge of the amino acids when the pH is at 1?
Overall positive
What happens to the charge of the amino aids when the pH is at 11
Overall negative
Are amino acids chiral molecules
Amino acids are chiral molecules
What is a chiral molecule
A chiral molecule cannot be superimposed on its mirror image. The property of being asymmetric
What are amino acids
20 incorporated into proteins. Classified by overall chemical properties of their side chains. They are nonpolar (hydrophobic), polar (uncharged), or charged (very polar).
What are the particularities of nonpolar amino acid side chains
Lack reactive functional groups. Have mainly hydrocarbon side chains
What are the nonpolar amino acid side chains
Alanine, Valine, Phenylalanine, Tryptophan, Leucine, Isoleucine, Methionine and Proline
What is the side chain of Alanine
CH3
What is the description of Alanine
Aliphatic R group (Methyl; Carbons and Hydrogens are not aromatic). Hydrophobic R group. Participates in hydrophobic interactions. Smallest chiral amino acid
What is the side chain of Valine
CH3-CH-CH3
What is the three letter format of Alanine
Ala
What is the three letter format of Valine
Val
What is the description of Valine
Aliphatic R group; Branched Carbon in the side chain. Highly hydrophobic R group.
What the side chain of Leucine
CH2-CH-CH3
-CH3
What is the three letter format of Leucine
Leu
What is the description of Leucine
Aliphatic R group; Branched. Highly hydrophobic R group. Participates in hydrophobic interactions
What is the side chain of Isoleucine
-H
C-CH2-CH3
-CH3
What is the the three letter format of Isoleucine
Ile
What is the description of Isoleucine
Aliphatic R group. Highly hydrophobic R group. Participates in hydrophobic interactions
What is the side chain of Phenylalanine
CH2-Benzene ring
What is the three letter format of Phenylalanine
Phe
What is the description of Phenylalanine
Aromatic R group. Highly hydrophobic R group. It is the highest hydrophobic R group of all amino acids. Participates in hydrophobic interactions
What is the side chain of Tryptophan
CH2 - NH pentene ring - benzene ring
What is the three letter formation of Tryptophan
Trp
What is the description of Tryptophan
Aromatic R group -heterocyclic. Mostly hydrophobic because it is bulky. Participates in hydrophobic interactions. Forms hydrogen bonds as a donor.
What is the side chain of Methionine
CH2-CH2-S-CH3
What is the three letter format of Methionine
Met
What is the description of Methionine
Aliphatic R group (it could be deemed honorary). Hydrophobic. Participates in hydrophobic interactions. Sulfur containing side group (thioether)
What is the side chain of proline
-CH2-CH2-CH2-
What is the three letter format of Proline
Pro
What is the description of Proline
Aliphatic side chain with distinctive cyclic structure. Secondary amino group. Hydrophobic but often found on protein surface because it has unique structural characteristics.
What are the particularities of polar amino acid side chains
Polar. Reactive due to presence of functional groups. Polar amino acids have side chains that contain an electronegative atom. Not all R groups have ionizable R group
What are the polar amino acids
Serine, Threonine, Tyrosine, Cysteine, Asparagine, Glutamine, Histidine and Glycine
What is the side chain of Glycine
H
What is the three letter format of Glycine
Gly
What is a description of Glycine
Achiral. Weakly polar. Small so it is flexible.
What is the side chain of Serine
CH2-OH
What is the three letter format of Serine
Ser
What is the description of Serine
Polar, uncharged. Contains hydroxyl group. Forms hydrogen bonds as an acceptor and donor; but it is typically a donor. Can be modified through phosphorylation
What is the side chain of Threonine
-OH
C-CH3
-H
What is the three letter format of Threonine
Thr
What is a description of Threonine
Polar, uncharged. Contains a hydroxyl. group, forms hydrogen bonds as an acceptor and donor but it is typically a donor. Can be phosphorylated
What is the side chain of Tyrosine
CH2-Benzene ring-OH
What is the three letter format of Tyrosine
Tyr
What is the pKa of Tyrosine
10.5
What is the description of Tyrosine
Weakly polar, uncharged. Aromatic R group, phenol and can participate in hydrophobic interactions. Contains hydroxyl group. Forms hydrogen bonds as an acceptor and donor; typically it is a donor
What is the side chain of Cysteine
CH2-SH
What is the three letter format of Cysteine
Cys
What is the pKa of Cysteine
8.5
What is the description of Cysteine
Polar, uncharged. Sulfur-containing side chain (thiol group - SH). Can form hydrogen bonds as a donor. Can form a thiolate anion (S-). Forms disulfide bonds with another Cysteine
How does Cystine form
Thiols in neighbouring cysteine resides can undergo oxidation to form a disulfide bond
What is Cystine
-NH3(+)(on the last CH)
(-)OOC-CH-CH2-S-S-CH2-CH-COO(-)
-NH3(+) (on the first CH)
What is the side chain of Asparagine
=O
CH2-C
-H2N
What is the three letter format of Asparagine
Asn
What is the description of Asparagine
Amide-containing side chain. Carboxamide functional group. Polar, uncharged. Forms hydrogen bonds as donor and acceptor. Nitrogen acts as donor and Oxygen acts as acceptor
What is the side chain of Glutamine
=O
CH2-CH2-C
-H2N
What is the three letter format of Glutamine
Gln
What is the description of Glutamine
Amide-containing side chain. Carboxamide functional group. Polar, uncharged. Forms hydrogen bonds. Nitrogen acts a donor and Oxygen acts as an acceptor
What is the side chain of Histidine
CH2-Heterocyclic (N and HN) pentene ring
What is the three letter format of Histidine
His
What is the pKa of Histidine
6.0. Side chain can be acidic or basic at neutral pH. Base form is predominant when pH is at or above 7.0. Acid form is predominant when pH is below 6.0
What is the description of Histidine
Polar, charged/uncharged. Histidine resides important in many enzyme catalyzed reactions. Proton donor (acid) / acceptor (base). Hydrogen bonding capability - proton donor or acceptor
What is the side chain of Aspartate
CH2-COO(-)
What is the three letter format of Aspartate
Asp
What is the pKa of Aspartate
4.0. Negatively charged R group at pH 7. Second carboxyl group. “Acidic” amino acid
What is the description of Aspartate
“Acidic” amino acid. Very polar. Forms hydrogen bonds, hydrogen bond acceptor. At pH 1 called aspartic acid.
Why does Aspartate change to Aspartic acid at pH 1
Contains a neutral functional group the COO(-) becomes COOH
What is the three letter format of Glutamate
Glu
What are the charged amino acids
Aspartate, Glutamate, Lysine, and Arginine
What are the negatively charged charged amino acids
Aspartate and Glutamate
What are the positively charged charged amino acids
Lysine and Arginine
What is the pKa of Glutamate
4.0. Negatively charged R group at pH 7. Second carboxyl group. “Acidic” amino acids.
What is the description of Glutamate
Very polar. Forms hydrogen bonds, Hydrogen bond acceptor. At pH 1 called glutamic acid
Why does Glutamate become Glutamic acid at pH 1
Contains a neutral functional group the COO(-) becomes COOH
What is the side chain of Lysine
CH2-CH2-CH2-CH2-NH3(+)
What is the three letter format of Lysine
Lys
What is the pKa of Lysine
10.0. Positively charged side group at pH 7. “Basic” amino acid
What is a description of Lysine
“Basic” amino acid. Side group contains an amino, so the total group contains 2 primary amino groups. Forms hydrogen bonds. It is a hydrogen bond donor and at pH 14 would be allow it to act as a hydrogen bond acceptor. Very polar
What is the side chain of Arginine
=NH2(+)
CH2-CH2-CH2-NH-C
-H2N
What is the three letter format of Arginine
Arg
What is the pKa of Arginine
12.5. Positively charged side group at pH 7. Guanido group. “Basic” amino acid. Never deprotonate under physiological conditions
What is a guanido group
Three nitrogen that are attached to a carbon
What is a description of Arginine
“Basic” amino acid. Never deprotonate under physiological conditions. Very polar. Forms hydrogen bonds as a donor and 5 are in the side chain.
What are the exceptions of the amino acids that don’t use the first three letters of their names
Asparagine (Asn), Glutamine (Gln), Isoleucine (Ile), and Tryptophan (Trp)
Where are polar side chains found
They are on in proteins on the surface because it can interact with water. It includes polar uncharged and polar charged amino acids
Where are the non-polar side chains found
Non-polar side chains are usually found buried in the protein core. Minimizes interactions with water (hydrophobic effect)
How do name when many amino acids joined together
Two peptides: dipeptide
Three peptides: tripeptide
Four peptides: tetrapeptide
etc.
What is a peptide/oligopeptide
General term for a larger number of amino acids, often refers to synthetic peptides (<40 residues)
What is a polypeptide
Produced by a translational process. Long chain of amino acids usually produced naturally.
What is a protein
Large polypeptide (or >1 polypeptide) with a biological function
What is a dipeptide
When you have Ser.Ala it is not equivalent to Ala.Ser. Sense of direction is important in distinguishing different molecules/and ulitmately sequencing. Direction is Nitrogen to Carbon by convention
What is a tetrapeptide
Only the terminal amino and carboxylate groups in a peptide retain their charge. The others are eliminated by the formation of peptide bonds. Side chains retain their charge (if they have one)
What is the backbone of a tetrapeptide
All non-sidechain R group atoms (Nitrogen-Carbon-Carbon-etc.)
What is the primary structure of proteins
The sequence of amino acids in a polypeptide is the “primary structure.” Covalent peptide bonds join each amino acid to the next. Every protein or polypeptide has a unique sequence
What are the characteristics of peptide bonds
They are rigid and planar
What are properties of peptide bonds
The electrons in peptide bonds are somewhat delocalized generating two resonance forms. Peptide bonds therefore exhibit double-bond character with no rotation around the C-N bond. The functional groups in peptide bonds are potential Hydrogen bond acceptors or donors
What happens because the peptide bonds are rigid and planar
The backbone of a polypeptide includes the Alpha carbon atoms and those involved in peptide bonds
What occurs in the folding conformations in proteins
Folding conformations are limited because two oxygens take the same space they minimize steric conflicts.
What are the hydrogen bonds in polypeptide backbones
The chemical groups found in peptide bonds are highly polar. Carbonyl groups are hydrogen bond acceptors. NH groups are hydrogen bond acceptors. They maximize their hydrogen bonding capabilities.
What are some secondary structures of proteins
Local folding of the polypeptide backbone. Allows for hydrogen bonding of the groups in the polypeptide backbone (C=O, N-H). “Regular” secondary structures occur when every amino acid in a segment of the polypeptide adopts the same geometry. A few regular patterns occur: alpha-helix and beta-sheet which both minimize steric conflicts and maximize hydrogen bonds
What occurs in an alpha-helix
The carbonyl oxygen of each residue forms a hydrogen bond with the backbone -NH group four resides downstream (C1…N5, C2…N6, etc). Complete hydrogen potential satisfied for backbone. Except for amino acid residues at either end all the backbone CO and NH groups are hydrogen bonded to one another in the helix. There is a right-handed twist.
What happens to the side chains in an alpha-helix
Helix is SOLID with atoms in the polypeptide backbone in Van der Waals contact with one another in the center. Amino acids project outwards residues 3-4 apart in the primary structure are close in the secondary structure
What are parallel and anti-parallel Beta-sheets
Multiple beta-strands are arranged side by side. Strands a joined by loops or other structures. Parallel strands appear to join diagonally and anti-parallel join vertically
How are beta-sheets drawn
They are often drawn as arrows. The arrows are shown pointing from the nitrogen-terminal to the carbon-terminal end.
How are anti-parallel sheets drawn
It flows from one arrow to other to form an easy zig-zag
How are parallel sheets drawn
The strands overlap because the arrows will be point the same direction.
Where are side chains located on a beta-sheet
Side chains are located above and below the plane of the sheet; they are alternating
What forces stabilize alpha-helices
Hydrogen bonds between the backbone CO and NH groups in the same helices
What forces stabilize beta-helices
Hydrogen bonds between CO and NH groups of neighbouring strands
What makes an irregular secondary structure
Distinct elements of regular secondary structure are linked together by polypeptide loops of various sizes ranging from simple hairpins to longer loops. These structures are irregular.
What is the tertiary structure of a protein
Arrangement of all atoms in a single polypeptide. Arrangement of secondary structure in relation to one another. Positions of amino acid side chains. Prosthetic groups (heme, FAD, etc.)
What are the two morphologies of tertiary protein structures
Fibrous (elongated) and Globular (compact)
What are fibrous proteins
Practically insoluble into aqueous solutions. Form long protein filaments - limited resides with repeats. Usually structural or connective proteins.
What are globular proteins
Practically soluble in aqueous solutions. Fold into compact structures with nonpolar cores and polar surfaces.
What structures do fibrous proteins adopt
Fibrous proteins (like collagen) tend to adopt linear extended structures
How variable is the structure of globular proteins
The tertiary structure in globular proteins is highly variable
Where are hydrophobic side chains found in a globular protein
Hydrophobic side chains are most likely to be found in the interior of a globular protein
Where are hydrophilic side chains found in a globular protein
Hydrophilic side chains are most likely to be found on the surface of a globular protein
Where are loops located in a globular protein
Loops tend to be located on the surface
Where are irregular structures located in a globular protein
Irregular structures are on the surface
Where are the regular structures located in a globular protein
Regular structures are in the core
What impacts the shape of the globular proteins
The shape of globular proteins depend of the relative positions of hydrophobic amino acids in the proteins primary structures
How does the hydrophobic effect have an impact on globular proteins
The hydrophobic effect is the “driving force” via which soluble globular proteins adopt and maintain their tertiary structure
What is Ion Pairs (“Salt Bridges”)
Electrostatic interactions between closely positioned formal charged groups. Like hydrogen bonds, these helps to “fine tune” and stabilize secondary and tertiary structures
What are the positive charges in ion pairs
N-terminus, Lys, Arg and His
What are the negative charges in ion pairs
C-terminus, Asp, Glu, Tyr and Cys
What can impact the charges of ion pairs
Charges will depend on pH of the environment
What is Disulfide bonds/bridges
Covalent bonds between closely positioned cysteines. These form stabilizing crosslinks for extracellular proteins (or proteins in the lumen)
What happens in the cytosol of Disulfide bonds/bridges
In the cytosol, cysteines do not oxidize to cystine as it is a reducing environment
What are the two main parts of protein structure
Domain and Motif
What is the domain of protein structure
A polypeptide segment that has folded into a single structural unit with a hydrophobic core. Proteins may contain more than one domain
What is the motif of protein structure
A short region of polypeptide with a recognizable 3D shape. Zinc fingers. May be found in many contexts
What are some examples of protein domains
Pyruvate kinase and Cow gamma crystalline
How many protein domains are in pyruvate kinase
It is composed of a single polypeptide chain, which can be divided into 3 domains
How many protein domains are in cow gamma cystalline
Contains two domains one polypeptide
What are some motifs in protein structure
Helix-loop-helix, Coiled coil, Helix bundle, Beta-alpha-beta unit, hairpin, beta-meander, greek key and beta sandwich
What are zinc fingers
An example of a structural motif including a prosthetic group.
What are prosthetic groups
A non-peptide component that is permanently incorporated into a protein
What are some examples of prosthetic groups
Zinc fingers and functional groups such as heme in hemoglobin
How are globular proteins impacted by outside forces
Globular proteins are stabilized by weak noncovalent forces and easily unfolded or “denatured” by heat, changes in pH, salt and detergents.
What can disrupt Disulfide bonds
Reducing agents (DTT) can disrupt disulfide bridges
What are quaternary structures
Proteins composed of more than one polypeptide chain. Each polypeptide chain is called a subunit.
How are quaternary structures named
Named by number and types of subunits.
2 subunits: Dimer
3 subunits: Trimer
etc.
What is the name of identical subunits in quaternary structures
Homodimer
What is the name of non-identical subunits in quaternary structures
Heterodimer
How are quaternary structures stabilized
They are stabilized by hydrophobic interactions and hydrogen bonds, ion pairs “fine-tune)
How is the function of a protein determined
The function of a protein is determined absolutely by its structure.
What is the name of the subunit of Myoglobin
Monomer with no quaternary structure
What is the name of the subunit of Hemoglobin
Oligomer with a quaternary structure
What is the role of Hemoglobin
Hemoglobin red blood cells binds O2 in the lungs and releases it in the tissues
What is the role of Myoglobin
Myoglobin binds O2 in muscle cells. Facilitates O2 diffusion through muscle tissue. Acts as a local reserve of O2 during intense exercise. Stores O2 in aquatic animals.
What is the role for both Hemoglobin and Myoglobin
Both bind oxygen reversibly but bind it with different affinities and under different conditions
What is the structure of Myoglobin
Polar propionyl groups. Porphyrin ring held in place by hydrophobic interactions AND by coordination bond between Fe2+ and a histidine which is called the proximal histidine
What does the proximal histidine do
- Binds heme into heme-binding pocket
2. Prevents oxidation of iron atom
What is the structure of heme
Heme is circular and planar. In heme, the porphyrin ring contains an Fe2+ ion coordinated between the four Nitrogen atoms. The two substituents at the bottom of the ring are polar (uncharged) propionyl groups whereas the rest are non-polar aliphatic groups
Where does Fe2+ ion position in Heme
5th coordination position
Where does O2 atom position in Heme
6th coordination position
What is the oxygen binding site in myoglobin
Binding sites are designed precisely to optimize binding specificity and affinity
How much stronger is the free Heme carbon monoxide affinity than O2
Free Heme Carbon monoxide affinity is ~2500 times higher than O2
How much stronger is Myoglobin / Hemoglobin carbon monoxide affinity than O2
Myoglobin / Hemoglobin carbon monoxide ~250 times higher than 02.
What are the two types of globin with within the tetramer of Hemoglobin
2 alpha subunits (alpha-globin) and 2 beta subunits (beta-globin)
What is the tertiary structure of beta-globin, alpha-globin and myoglobin
All 3 polypeptides comprise 8 alpha-helices with a heme binding pocket between helices E and F (plus irregular structures).
How much of the primary structure is approximately identical
20-25% identical
What are homologous proteins/polypeptides
They share an ancestral heritage
What is the composition of hemoglobin (Hb)
4 polypeptide chains, 2 alpha-globin chains, 2 beta-globin chains and 1 heme/polypeptide - binds 4 O2/Hb
What is the composition of Myoglobin
1 polypeptide chain, 1 heme - binds 1 O2/Mb
What are conservative substitutions
Relatively minor effects on structure/function. Examples are: Leu and Ile, and Thr and Ser
What are critical substitutions
Change structure and function depending on location. Examples are: polar to nonpolar, Ser and Val, and Phe and Lys
How does the alpha-subunit and beta-subunit of hemoglobin binds O2 in the same manner as myoglobin
Oxygen at the 6th coordination position of an Fe2+ ion in a heme ring
What are the critical resides that are invariant
Several critical residues in/near the oxygen binding are invariant (do not change) among the three polypeptides: -His F8, and - His E7
What does a hyperbolic curve indicate
Hyperbolic curve is indicative of constant affinity
What is an example of a hyperbolic curve
Myoglobin
What is a sigmoidal curve
A sigmoidal curve is diagnostic of cooperative binding affinity
What is an example of sigmoidal curve
Hemoglobin
What is the function of Myoglobin and Hemoglobin
Reversibly bind/release O2
What is the function of Myoglobin that is different than Hemoglobin
O2 transport within tissue
What is the function of Hemoglobin that is different than Myoglobin
O2 transport from lungs to tissues
What is the point of the sigmoidal binding curve
Cooperative process (positive cooperativity), necessary for efficient O2 delivery, and reflects change in binding affinity; change in tertiary structure and quaternary structure of hemoglobin
How does Hb change its affinity for O2?
Two Distinct Structures of Hemoglobin, T state or R state
What does T state look like
In the T state, in deoxyhemoglobin, a His residue on the beta subunit fits between a Thr and a Pro residue in the alpha-subunit
What does R state look like
In the R state, upon oxygenation, the hemoglobin changes shape and the His residue is now located between two Thr residues on the alpha subunit
What is the O2 affinity to T state
Low affinity for O2
What is the O2 affinity to R state
High affinity for O2
Does T state or R state have deoxy hemoglobin
T state
Does T state or R state have oxy hemoglobin
R state
What size is the central cavity of T state
Larger central cavity
What size is the central cavity of R state
Smaller central cavity
What does Allostery mean
“Other” “Space”
What are allosteric effectors
Compounds which, upon binding, alter affinity at other binding sites
What is Homoallosteric
Binding of the effector affects further binding of the same compounds
What is Heteroallosteric
Binding of the effect affects further binding of the different compound
What are activators in allostery
Increase binding affinity they are positive effectors
What are inhibitors in allostery
Decrease binding affinity they are negative effectors
What is the Action of Allosteric Effectors
Equilibrium between T and R is being affected by the binding of X. The binding of a ligand/substrate at one site on a macromolecule affects the affinity of other sites for the SAME ligand.
What are the conformational changes in oxygen binding to hemoglobin
The iron moves into plane of heme (when they are changing from T state to R state). The proximal histidine moves with the iron atoms
What are the events in O2 binding to Hemoglobin
T-state (no O2 bound). O2 binds to a subunit.. Fe2+ moves into plane of heme. Histidine F8 moves with iron. Helix F moves, Subunit interface changes. Subunit interface change affects other subunits. Helix F/His F8/Fe2+ movement. Oxygen binding site becomes high affinity (R). Oxygen binds more readily to other binding sites
What kind of allosteric effect does O2 have
O2 is a homoallosteric activator
What kind of allosteric effect does BPG have
BPG is a heteroallosteric inihibiter (for O2)
What is BPG
2,3-bisphophoglycerate
What kind of allosteric effect does H+ have
H+ is a heteroallosteric inhibitor (for 02)
What does BPG and H+ do in the T state
BPG and H+ stabilize T state they are both part of the ‘Bohr effect’.
How is BPG essential to the T state of Hemoglobin
Small and highly negative. Negative Allosteric Effector of O2 binding
How does BPG bind to Deoxyhemoglobin
BPG binds in the central cavity of the deoxyhemoglobin (T state). The negative charges on the BPG interaction with positively charged groups on the protein that are directed into the central cavity. 4 His, 2 Lys, 2 N-terminal residues The central cavity in oxyhemoglobin (R state) is too small to accommodate BPG.
What is the result of metabolism generating protons
It lowers pH
Examples:
ATP + H2O → ADP + Pi + H (+)
CO2 + H2O → HCO3 (-) + H (+)
What does lowering pH lead do to side chains and functional groups
Lowering pH leads to protonation of side chains and functional groups
Examples:
His + H (+) → His (+)
NH2 + H (+) → NH3 (+)
What does the Bohr Effect do
pH dependence of O2 binding. As we lower the pH oxygen affinity decreases. As we raise the pH oxygen affinity increases
In the lungs and in the tissues how does Hemoglobin exist
In the lungs and in the tissues, any given molecule of Hb can exist in either the T state or the R state. The lungs have a high pp O2 and a relatively high pH. The R state is thus favoured, and when oxygen binds it triggers the switch to the R form. Actively respiring tissues have a relatively low pH and a low pp O2. The T state is favoured, and oxygen is released.
What affects the proportion of molecules
Their proportion of molecules that are in either form (the position of the equilibrium) depends on the presence of BPG, on the [H+] ions, and on the pp O2. The proportion of molecules that are in either form (high or low affinity) determines how much oxygen is bound or released.
How do sickled red blood cells come to be
B-chain Glu6 is replace with Val. (Polar charged amino acid change with to a nonpolar amino acid) Critical substitution
What are the effects of the sickle mutation
In Hb there is a small hydrophobic surface patch which is exposed between the E and F helices during the transition from R to T form. The hydrophobic Val binds here, causing the Hb molecules to aggregate into long polymers/fibres.
What is Fetal Hemoglobin
2 alpha and 2 gamma subunits. (Gamma subunit replaces the Beta subunit.) Gamma subunit is the adult beta subunit. (Homologous (73% identical to Beta subunit). Substitution of His143 with serine) His143 is one of the His residues that is involved in binding BPG. (Decreased BPG affinity. Increased O2 affinity)
What are the roles of HisF8 (proximal histidine)
Attachment of heme. Prevent oxidation of Fe2+
What is the roles of HisE7 (distal histidine)
Assist O2 binding. Decreases affinity of CO
What do the 4 Histidine in the central cavity and subunit interface do
4 His in the central cavity and the subunit interface are part of the “Bohr effect.”
