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60 Cards in this Set
- Front
- Back
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Proteins that bind to foreign substances and eliminate them from the organism
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Antibodies
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Describe the immunoglobulin structure
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2 heavy chains and 2 light chains (held together by 3 disulfide bonds)
Variable and constant regions (both light and heavy chains have variable regions) |
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What makes immunoglobulins glycoproteins?
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Carbohydrates are attached to C2 of the heavy chain (this is part of what makes it heavy)
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Production of antibodies is induced by ____________.
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Antigens
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Each human can potentially produce ___________ (#) different antibodies.
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100 million
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Which part of the immunoglobulin determine the class? Where does the antigen bind?
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C regions ;
V regions |
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Within the variable regions of immunoglobulins are hypervariable regions called _________________. These complement and bind the topology of the antigen using (covalent/ noncovalent) bonding.
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complementarity-determining regions (CDRs);
noncovalent |
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Which part of an Ig binds complement proteins which lyse invading cells?
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C region
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Which part of an Ig contains the binding site necessary to cross the placental membrane?
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C region
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Explain Ig folds
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Ig contains 7-9 beta-strands arranged into 2 antiparallel sheets. There are 12 folds in each antibody.
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Proteolytic enzymes are classified according to their ____________ mechanism
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catalytic
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Proteases that cleave peptide bonds on the interior of a polypeptide are called _____________.
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Endopeptidases
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Proteases that cleave peptide bonds on the exterior of a polypeptide (the N-terminus or the C-terminus) are called _____________.
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exopeptidases
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How are serine proteases identified? Which serine is involved in serine proteases?
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An irreversible reaction of active site Ser with diisopropylfluorophosphate (DFP). DFP will only react with Ser195, NOT all of the side chains containing Ser.
Ser195 |
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Which three AA make up the catalytic triad of serine proteases
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Asp102, His57, Ser195
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Explain what happens in the catalytic triangle after a substrate containing the bond to be cleaved binds to a serine protease.
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Once Ser195 is bound, Asp102 forms a low barrier H-bond with His57 (this changes the pKa of His 57 from 7 to about 12) His 57 is now able to deprotonate Ser195. This leaves Ser195 as a strong nucleophile to break peptide bonds
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All serine proteases are numbered according to ________________ so that the catalytically active Ser is always Ser195, regardless of its position in the peptide.
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Chymotrypsinogen
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Enzyme that cleaves peptide bonds (scissile bonds)
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Serine proteases (really just proteases in general)
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All serine proteases are synthesized as _____________. These are inactive until activated by limited proteolysis.
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Zymogens (contains -ogen or the prefix pro-). When the zymogen is cleaved to the active form the name changes.
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How si specificity of serine proteases determined?
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By binding the substrate aas (Ps) to enzyme subsites (Ss) using noncovalent interactions.
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Serine Protease that forms soft blood clots
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Thrombin (factor II)
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Serine protease that is called the "christmas factor" and deficit causes hemophilia A
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Factor VIII
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Serine protease that activates thrombin
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prothrombinase (factor X)
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Serine protease that is a thrombolytic agent. What does it activate?
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TPA (tissue plasminogen activators)
Activates plasminogen to convert to plasmin |
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Plasmin
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Lyses blood clots
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Where does trypsin cleave during digestion?
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The carboxyl side of Arg and Lys
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Where does chymotrypsin cleave during digestion?
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The carboxyl side of Tyr, Trp, and Phe
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What is a serine protease inhibitor called?
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Serpin
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What inhibits factor II
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antithrombin III
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What inhibits plasminogen activator?
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plasminogen activator inhibitor
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What inhibits plasmin?
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alpha2- antiplasmin
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What is the symbol for adult hemoglobin? Fetal?
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HbA1; HbF
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What chains does fetal Hb have? Which has a higher affinity for O2, HbF or HbA1?
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2 alpha, two gamma
HbF |
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What substrates can Hb carry?
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O2, CO2, and NO
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Each Hb chain contains a ___________ and can bind an O2
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globin fold
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Where is myoglobin found? How many chains?
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Mb is found in the sarcoplasm of skeletal muscle. 1 chain (therfore, 1 fold and 1 O2)
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What is a prosthetic group?
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A nonpolypeptide moeity that forms a functional part of a protein
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A protein without its prosthetic group is called?
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Apoprotein
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A protein with its prosthetic group is called?
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Holoprotein
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The helices of Hb are lettered ______ thru ______ beginning with the ____ terminus
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A thru H
N-terminus |
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what is the N terminus denoted in Hb? the C terminus?
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NA
HC |
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the heme group contains 4 ____ rings with what side chains? What does all of this make up (pyrrole rings plus the side groups)?
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pyrrole
4 methyl 2 proprionate 2 vinyl protoporphyrin IX ring |
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Match the following :
beta folds globin folds catalytic triad Hb Serine proteases Ig |
Ig= Beta folds
Hb= globin folds serine proteases= catalytic triad |
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What makes up the "hydrophobic pocket" of Hb? What is this significance?
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His E7 (the distal His) and Val E11 form a hydrophobic pocket.
This prevents H2O from binding, but allows O2 to bind |
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What surround the Heme in Hb?
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About 80 different interactions and a hydrophobic pocket (made up of the distal His E7 and Val E11)
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Does the iron changes the oxidation state when O2 binds?
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NO (it is in the ferrous (FeII) state when penta- and when hexa-coordinated)
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A hyperbola-like graph might indicate:
a) binding of O2 to Mb b) binding of O2 to Hb |
a) binding of O2 to Mb
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A sigmoid graph might indicate :
a) binding of O2 to Mb b) binding of O2 to Hb *also, what does the sigmoid graph indicate? |
b) binding of O2 to Hb
**positive cooperativity |
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What is positive cooperativity (simple)
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Once one O2 binds to Hb, the other subunits bind O2 more easily
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Deoxyhemoglobin is in the (R/T) state.
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T
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Oxyhemoglobin is in the (R/T) state
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R (Fe is pulled out of the porphyrin ring plane by about 0.5 angstroms
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What happens to ferrous in oxyhemoglobin (in terms of the electron cloud)?
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The electron cloud shrinks, and the smaller ferrous is pulled down into the porphyrin ring into the relaxed state.
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What happens to the salt bridges in oxyhemoglobin?
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They break (this causes the positive cooperativity
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The ______ corner of on chain of hemoglobin is packed against the _-helix of a second chain
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FG
C |
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~80 % of the CO2 produced by metabolizing cells is transported to the lungs by _____________. This is enzyme (independent/ dependent) transport
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isohydric transport.
dependent |
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~20 % of the CO2 produced by metabolizing cells is transported to the lungs by _____________. This is enzyme (independent/ dependent) transport
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carbamino-hemoglobin
independent |
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Where does CO2 bind to in carbamino-hemoglobin?
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CO2 + HbNH2 --> HbNH-CO2 + H
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What are the AAs that are involved in the release of the proton during oxygenation of hemoglobin?
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Asp94 and His 146
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What part of the Hb molecule does NO bind to? When is it able to do this and how?
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No is initially taken up by the Fe on the alpha chain while in the T conformation. Once O2 binds to the beta, the transformation from the T to the R conformation causes the beta Asp-94 and the His-146 to break bonds and the S of the cysteine is able to form the Cys-S-NO complex which swings inward once in the R conformation
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When does NO become unattached from Hb? And what protein "picks it up"?
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Once the O2 reaches the acidic site where it needs to unload the O2, the conformation into the tense state again causes the Cys-93 to swing back out, exposing NO.
Glutathione picks up the NO. (causes vasodilation) |
