50. Protein structure Flashcards by iya gerzon

set of all proteins expressed by an individual cell at a particular time

proteome

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aims to identify the entire complement of proteins elaborated by a cell under diverse conditions

proteomics

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except for this aa, each amino acids has a
•carboxyl group
•amino group
•R group

proline

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this amino acid is a major inhibitory neurotransmitter in the spinal cord

glycine

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constitutes as a major fraction of free amino acids in the blood

alanine

glycine

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Valine
Leucine
Isoleucine
acuumulate in this disease

maple syrup urine disease

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precursor of tyrosine

phenylalanine

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precursor of homocysteine

methionine

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involved in transfer of methyl groups as S-adenosylmethionine (SAM)

methionine

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imino acid

proline

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contributes to the fibrous structure of collagen

interrupts alpha helices in globular proteins

proline

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site of O-linked glycosylation

serine
threonine
tyrosine

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precursor of dopamine and epinephrine

tyrosine

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precursor of thyroxine and melanin

tyrosine

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site for N-linked glycosylation

asparagine

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major carrier of nitrogen to the liver from peripheral tissues

glutamine

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carrier of ammonia from skeletal muscle to the liver

alanine

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precursor of GABA and glutathione

glutamate

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precursor of histamine

histidine

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used in diagnosis of folic acid deficiency

histidine (FIGIu excretion test)

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precursor of creatinine, urea, nitric oxide

arginine

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implicated in neurolathyrism

* progressive and irreversible spastic paralysis of lower extremities

Homourginine,

ß-N-Oxalyldiaminopropionic acid

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neurotoxic amino acid in Cycad seeds

* implicated in ALS-Parkinson dementia complex in natives of Guam

ß-methylaminoalanine

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amino acid considered nutritionally semi-essential

arginine

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amino acid that can be synthesized the body

cystine | tyrosine

sequencing from N-terminal amino acid

•Sanger’s reagent (1-fluoro-2,4-dinitrobenzene) | Edman’s reagent (Phenylisothiocyanate)

sequencing from C-terminal amino acid

* Hydrazine | * carboxypeptidases

secondary structure of proteins is stabilized by

hydrogen bonding

most common secondary structurte

alpha helix

supersecondary sructures produced by packing side chains from adjacent secondary structural elements close to each other

motifs

overall 3-dimensional shape of the protein

tertiary strucrure

this protein structure is stabilized by disulfide bonds, hydrophobic interactions, hydrogenm bonds and ionic interactions

tertiary structure

fundamental functional and 3 dimensional structural units of polypeptide

domains

number and types of polypeptide units of oligomeric proteins and their spatial arrangement

quaternary structure

results in unfolding and disorganization of the protein’s secondary and tertiary structures

denaturation

rescue proteins | required for proper folding of many species of proteins

chaperones

fatal neurodegenerative diseases characterized by: | •spongiform changes, astrocytic gliomas, neuronal loss

prion diseases

* most common and most important degenerative disease of the brain * diffuse cerebral atrophy with dementia * senile plaques and neurofibrillary bundles * aggregates of protein ß-amyloid

Alzheimer disease

this lipoprotein has been implicated as a potential mediator transformation of soluble alpha helix rich state to beta amyloid that is prone to self-aggregation

apolipoprotein E

configuration of Hemoglobin with low O2 affinity

Taut form (T form)

configuration of Hemoglobin with high O2 affinity | 300 X

R form (relaxed)

O2 dissociation curve shows saturation

myoglobin

O2 dissociation curve shows cooperativity

hemoglobin

has allosteric effects a. myoglobin b. hemoglobin

b hemoglobin

factors that cause shift to the right of O2 dissociation curve

* ÎÎ CO2 * ÎÎacidity (dec pH) * ÎÎ 2.3 BPG * ÎÎ exercise * ÎÎ Temp

stabilizes the T structure of Hgb by forming additional salt bridges taht must be broken down prior to conversion to the R state

2,3-BPG

refers to the observation that increases in the carbon dioxide partial pressure of blood or decreases in blood pH result in a lower affinity of hemoglobin for oxygen.

Bohr effect

results from the fact that deoxygenated hemoglobin has a higher affinity (~3.5 x) for CO2 than does oxyhemoglobin. Deoxygenated hemoglobin has a higher affinity for CO2 because it is a better proton acceptor than oxygenated hemoglobin. Therefore, when hemoglobin is deoxygenated (i.e., at tissues) there is a right shift of the carbonic acid-bicarbonate buffer equation to produce H+ which in turn increases the amount of CO2 which can be carried by the blood back to the lungs to be exhaled. Then, with oxygenation at the lungs CO2 dissociates more readily from hemoglobin.

Haldane effect

ζ2 ε2

Embryonal hemoglobin (Hb Gower 1)

α2 γ2

Fetal hemoglobin (HbF)

α2 ß2

Hemoglobin A (HbA)

α2 δ2

Hemoglobin A2

conception up to first few months

Hb Gower 1

First few months to after birth

HbF

8 month onwards

HbA

cutoff of HbA1C to diagnose DM

≥ 6.5%

lowering A1C below ____ has been shown to reduce microvascular and neuropathic complications of DM

for microvascular disease prevention, the A1C goal for nonpregnant adults is

<7%

when blood glucose enters erythrocytes, it glycosylates

* ε- amino group of lysine residues | * amino terminals of Hgb

has 200 x greater affinity for Hgb than O2

Tx for carboxyhemoglobin

100% O2 therapy

oxidized form of Hgb (Fe3+) that does not bind O2, but has higher affinity for cyanide

methemoglobin

s and sx of methemoglobinemia

anxiety headache dyspnea O2 sat: 85%

chocolate cyanosis

methemoglobinemia

tx for methemoglobinemia

Mild: oral methylene blue or ascorbic acid •Acute massive due to ingesiton: IV methylene blue

disorder characterized by inherited defect in RBC membrane that renders the erythrocytes speroidal, less deformable and vulnerable to splenic sequestration and detruction

hereditary spherocytosis

mutations associated with hereditary spherocytosis

* ankyrin (most common) * spectrin * band 4.1 * band 3

hereditary spherocytosis | manifestations

* anemia * splenomegaly * jaundice

lab test for hereditary spherocytosis

osmotic fragility test

inheritance of sickle cell disease

homozygous recessive disorder

results from a point mutation in both genes coding for ß chain that results in a VALINE rather than GLUTAMATE

Sickle cell disease

* polymerization and dec solubility of the deoxy form of Hb * distortion of the RBC membrane * Misshapen, rigid RBC occlude capillaries

sickle cell disease

manifestations | Sickle cell disease

anemia tissue anoxia painful crises protective against malaria

tx sickle cell disease

hydration analgesics antibiotics if with infection , transfusions, hydroxyurea

Hgb C disease | Hgb variant that has a single amino acid substitution in ____

6th position of the ß-globin chain | •lysine- substituted for glutamate

inadequate synthesis of alpha chains | •symptoms appear at birth

alpha thalassemia •alpha chains needed for HbF and HbA

leads to anemia, accumulation of Hb Bart (y4) ad Hb H (ß4) and ß chain precipitation

alpha thalassema

inadequate synthesis of beta chains

Beta thalassemia

* symptoms appear after birth | * leads to anemia, accumulation of Hb Barts and alpha chain precipitation

Beta thalassemia