-
molecule bound reversibly by a protein
ligand
-
structural adaptation that occurs between ligand and protein to make the binding site more complementary to the ligand
induced fit
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# of polypeptide chains Hb contains (& types)
4
2  -chains, 2 -chains
-
what binds to O2 in Hb?
each polypeptide chain contains 1 heme group that binds
-
If a ligand specifically binds to one of the 2 states, equilibrium between those states will be shifted in favor of the state with bound ligand with the increase of ligand concentration
Wyman Linkage relationship
-
cyclic organic ring structure bound to Fe to generate heme
protoporphyrin
-
what state of Fe binds to oxygen?
Fe2+
-
what prevents the conversion of ferrous iron Fe2+) to ferric (Fe3+)?
the 4 nitrogen atoms bound to Fe in heme
-
2 conformations of Hb
- 1) T state - low O2 affinity
- 2) R state - high O2 affinity
-
conformational change in Hb R state
subunit pairs slide past each other and rotate, narrowing the pocket between the subunits
-
2 axial ligands to Fe in heme
- 1) sidechain N of a His residue
- 2) O2 binding site
-
equation for the fraction of total binding sites occupied in Hb
-
protein in which the binding of a ligand to one site affects the binding properties of another site in the same protein
allosteric protein
-
Hill coefficient nH>1
positive cooperativity
-
positive cooperativity
ligand binding at one site promotes the ligand binding at another site
-
Hill coefficient nH=1
no cooperativity
-
negative cooperativity
binding of one ligand impedes the binding of others
-
any molecule capable of eliciting an immune response
antigen
-
percentage of blood protein made up of antibodies
20%
-
5 classes of antibodies
- 1) IgG
- 2) IgA
- 3) IgD
- 4) IgE
- 5) IgM
-
major class of antibody
IgG
-
antibody found in saliva, tears, and milk
IgA
-
3 fragments of IgG when cleaved by papain
- 1) Fc (constant Ab stem)
- 2) 2 Fab's (antigen-binding fragments
-
a particular molecular structure within an Ag that binds to an individual antibody or TCR
antigenic determinant/epitope
-
what is binding specificity of an antibody determined by?
amino acid sequences in the variable domains
-
what activates the macrophage to engulf a foreign body?
IgG binding to an antigen -> receptors on the macrophage surface recognize and bind the Fc region of IgG
-
proteins that interact with partially folded or improperly folded polypeptides, facilitating correct folding pathways
chaperones/chaperonins
-
what to chaperones bind to on improperly folded proteins?
regions rich in hydrophobic residues
-
do chaperones actively promote folding of a protein?
no, they just prevent aggregation
-
what is the difference between chaperones and chaperonins?
chaperonins provide a cavity for the folding of an isolated substrate (ex: GroEL/GroES)
-
GroEL
double donut shaped protein, with 7 polypeptide chains per donut (14 total)
-
two-stroke system
during 1 cycle, 2 substrate molecules are folded
-
when does the conformational change occur in the GroEL/ES system?
GroES binding to one of the GroEL rings
-
where is the chemical energy for muscle contraction derived from?
ATP hydrolysis
-
percentage of protein mass of muscle actin and myosin make up
80%
-
motor domain that makes muscle contraction possible
myosin head group (globular domain)
-
myosin subunits
- - 2 heavy chains
- - 4 light chains
-
myosin heavy chain structure
@ C-term: extended helices, wrapped around each other in a left-handed coiled coil
@N-term: each chain has a large globular domain containing an ATP hydrolysis site
-
location of myosin light chains
associated with the globular domains of heavy chains
-
myosin aggregates in muscle cells
thick filaments
-
bipolar structure of a thick filament
several hundred myosin molecules associate their fibrous tails, with globular domains projecting from either end
-
thin filament makeup
F-actin (+ other proteins)
-
F-actin
filamentous actin
associated globular actin (G-actin) proteins
-
binds ATP and hydrolyzes it to ADP, which helps in the assembly of filaments
G-actin (globular actin)
-
binds tightly and specifically to 1 myosin head group
each actin monomer in the thin filament
-
slide along actin thin filaments during contraction
myosin thick filaments
-
what causes dissociation of myosin head from actin?
ATP binding to myosin head
-
conformational change in the myosin head that moves actin and myosin filaments relative to one another
power stroke
-
triggers power stroke
Pi release from the myosin head
-
structure serving as an anchor to which thin filaments are attached
Z disk
-
arises from the thick filament
A band
-
arises from the thin filaments
I band
-
during contraction, Z disks in neighboring __bands draw closer together
I bands
-
# heme groups in myoglobin
1
-
myoglobin cooperativity
nH=1, since there is only 1 ligand binding site
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