8) Proteins Flashcards
basic protein formula
RCH(NH2)COOH
isoelectric point (pI)
the pH at which the amino acid or protein has no net charge, and the positive charges equal the negative charges
At a pH ——– than the pI, the protein carries a ——– charge
greater – negative
less – positive
peptide bond
Chemical bond between a carboxyl group of one molecule and an amino group of the other molecule, releasing water
Plasma ——— provided by the proteins tends to retain water in the vascular space
colloid osmotic pressure (COP)
3 main functions of plasma proteins
- Maintenance of water distribution between cells and tissue.
- Coagulation proteins are important in maintenance of hemostasis.
- Transport vehicles to move various ligands to where they are needed or stored.
Rare inherited disease involving the homogentisic acid oxidase
Leads to a buildup of homogentisic acid in the tissues of the body
alkaptonuria
darkening of the tissues of the body because of the excess homogentisic acid
Ochronosis
Caused by the absence or very low levels of the branched-chain enzyme α-keto acid decarboxylase complex
MSUD
Results in the abnormal metabolism of three essential amino acids:
leucine, isoleucine, and valine
MSUD
Results in the inability to metabolize the essential amino acid phenylalanine
phenylketonuria
grouping of plasma proteins
- Albumin
- Globulin (α1 globulins, α2 globulins, ß1 globulins, λ globulins)
TP =
albumin + globulin
Main clinical significance of ———- is role as a sensitive marker of poor nutritional status such as protein-energy malnutrition (PEM).
prealbumin/transthyretin (TTR)
protein measured in CSF, not electrophoresis
prealbumin/TTR
albumin is approximiately —-% of serum protein
60
list the 16 plasma proteins
𝛼1 - 3
𝛼2 - 3
β - 5
𝛾 - 2
prealbumin
albumin
—
𝛼1-antitrypsin
𝛼1-acid glycoprotein
alpha-fetoprotein
—
haptoglobin
ceruloplasmin
𝛼2-macroglobulin
—
transferrin
hemopexin
β-lipoproteins
β2-microglobulin
C3
—
fibrinogen
—
C-reactive protein
Ig
albumin functions
Maintain plasma colloid osmotic pressure.
Bind and transport a wide variety of ligands.
Serve as an endogenous source of amino acids.
causes of hypoalbuminemia
- increased catabolism (most common)
- impaired synthesis
- increased protein loss
- analbuminemia
causes of hyperalbuminemia
- Dehydration/decreased plasma volume
- high protein diet
- albumin infusion
A/G ratio
albumin/globulin
globulin = TP - albumin
RR for A/G ratio
0.8-2.2
Major α1–globulin, making up approximately 90% of α1–proteins.
α1–Antitrypsin (AAT)
one of the most common genetically lethal diseases in Caucasians (1:4000)
AAT deficiency
sx of AAT deficiency
emphysema with onset at 45 years of age or earlier
emphysema occurring in the absence of smoking
is the major glycoprotein increased during inflammation, an Acute Phase Reactant (APR).
α1–Acid Glycoprotein/orosomucoid
(AAG)
Principal fetoprotein (fetal albumin-like protein) in maternal serum
alpha-fetoprotein
Used to screen for the antenatal diagnosis of neural tube defects including spina bifida and anencephaly
AFP
—— is decreased in Down’s syndrome and Trisomy 18
AFP
increased levels found in 80% of patients with hepatocellular cancer, 50% of germ cell tumors (gonadal), and all children with hepatoblastoma
AFP
An acute phase reactant that binds free hemoglobin in plasma
haptoglobin (Hp)
Depletion is the most sensitive indicator of intravascular hemolysis, in transfusion reactions, and certain hemolytic anemias.
Hp
Principal copper (Cu)-containing protein in plasma containing 95% of the total serum copper
Ceruloplasmin (Cp)
Decreased in Wilson’s disease, Menkes disease, malnutrition, malabsorption, severe liver disease, nephritic syndrome
Cp
Rare autosomal recessive trait where Cp levels are reduced and the dialyzable Cu concentration is increased.
Wilson disease
copper chealators used to tx Wilson’s
penicillamine
trientine
effects of Wilson’s disease
- Degenerative cirrhosis
- Chronic active hepatitis
- Renal tubular acidosis
- Neurological damage (clumsiness, tremors)
- Kayser-Fleischer rings, pigmented rings at the outer margins of the cornea and the sclera
In nephrotic syndrome, —— is characteristically increased above normal because it is retained while smaller proteins are excreted in the urine.
AMG
Major component of β-globulins
negative acute phase reactant
TRF
Principal plasma protein for transport of iron as Fe+3 — the ferric ion — to storage sites, where it is bound to apoferritin and stored as ferritin
TRF
Important in the differential diagnosis of anemias and monitoring the treatment of iron deficiency anemia
TRF
A commonly used indicator of iron overload—screen for hemochromatosis
TRF
When red blood cells are destroyed, it transports heme to the liver, where it is catabolized by the reticuloendothelial system.
hemopexin
Increased levels are found in pregnancy and in diabetes mellitus.
hemopexin
Comprises the common light chain of human leukocyte antigens (HLA) found in all nucleated cells
BMG
Used for staging MM and for CLL survival
BMG
Increased in renal failure, inflammation, and neoplasms—especially those associated with B-lymphocytes
BMG
Collective term for 30 glycoproteins that participate in the immune reaction and serve as a link to the inflammatory response
C3
Plasma — sharp peak between Beta and Gamma region on electrophoresis (artifact)
fibrinogen
absent in serum
An acute phase reactant and a nonspecific indicator of bacterial vs viral infection, inflammation, and tissue injury or necrosis
CRP
Reacts with proteins present in many bacteria, fungi, and protozoan parasites
CRP
Levels rise dramatically following myocardial infarction, trauma, psychological or physical stress, infection, inflammation (e.g., rheumatic fever, rheumatoid arthritis), surgery, and various cancers.
CRP
undetectable in healthy individuals
CRP
Spike in Waldenstrom’s Macroglobulinemia
IgM
can rarely see an —– spike in MM
IgA
Increased in infections, liver disease,
connective tissue disorders
IgD
—– proteins move toward the cathode (right)
gamma
Transitory ——— elevations in pre-eclampsia of pregnancy and dehydration.
urinary protein
indicator in protein pad of urine strip
tetrabromophenol blue
urinary protein elevation causes
pregnancy
nephritic syndrome
acute and chronic glomerulonephritis
renal failure
lesions of the kidney
multiple myeloma
RR for CSF protein
15-45 mg/dL
Increased CSF protein levels indicate…
a broken blood/brain barrier
Associated with a positive nitrogen balance
hyperproteinemia
(hemoconcentration or dehydration)
characteristic electrophoresis pattern of MM
monoclonal spike in gamma region
Caused by a negative nitrogen balance
hypoproteinemia
Based on presence of peptide bonds found in all proteins.
biuret reagent
When a solution of protein (serum or plasma) is treated with cupric (Cu+2) divalent ions in a moderately alkaline medium, a violet-colored chelate, which absorbs light at —– nm, is formed between the cupric ion and carbonyl oxygen and the amide nitrogen atoms of the peptide bond.
540
Sodium potassium tartrate
Copper sulfate
Potassium iodide
NaOH
biuret reagent
dye-binding method of protein analysis uses ———-, which is dissolved in an acidic solution, causing it to absorb at 465 nm
Coomassie Blue G-250
RR for serum protein
6.0-8.3 g/dL
A physiological decrease of approximately 0.5 g/dL protein occurs in …..
bedridden patients
2 methods used for albumin
Bromocresol green
Bromocresol purple
4 requirements for dye-binding albumin methods
- Specific binding of the dye to albumin in the presence of serum or plasma proteins
- High binding affinity between the dye and albumin
- Substantial shift in the absorption wavelength of the dye in the bound form
- Absorption maximum for the bound form at a wavelength distinct from those where bilirubin and hemoglobin, the main interfering chromogens, can interfere
zwitterion
A molecule or ion having separate positively and negatively charged groups, with net zero charge
relative protein %
relative % = absorbance of one band/absorbance of all bands
high resolution electrophoresis
divides Beta band into 2
Electrophoresis pattern shows a double albumin spike
bisalbuminemia
a condition in which abnormal proteins (antibodies) of one type are found.
monoclonal gammopathy
a condition in which results from an increased production of several different immunoglobulins.
polyclonal gammopathy
- Patient’s serum has an M-protein that measures <3 g/dL
- Bone marrow that contains <10% of plasma cells
- no CRAB
Monoclonal Gammopathy of Undetermined Significance (MGUS)
- Patient’s serum has an M-protein that measures ≥3g/dL
- Bone marrow that contains ≥10% of plasma cells
- no CRAB
Smoldering Multiple Myeloma (SMM)
Plasma cells light chains (pieces of antibodies) misfold and build up in organs, causing them to thicken and loose function
amyloid light-chain (AL) amyloidosis
associated with SMM
Neoplastic proliferation of a clone of plasma cells
multiple myeloma
b cell tumor
plasmacytoma
hallmark of MM
lytic bone lesions
free light chains in urine associated with MM
Bence Jones proteins
Calcium (hypercalcemia)
Renal insufficiency
Anemia
Bone lesions/pain
Overproduction by B lymphocytes, mainly in lymph nodes
Waldenstrom’s Macroglobulinemia (WM)
Starts with an IgM MGUS
WM
Enlarged lymph nodes
Rouleaux formation on peripheral smear
↑ ESR
WM
Can precipitate and act as a cryoglobulin at low temperatures
Raynaud’s phenomenon
cold urticaria
WM
Can lead to Hyperviscosity syndrome
WM
adverse effects of hyperviscosity syndrome
- Bleeding/vascular insufficiency
- Visual impairments
- Cardiac Insufficiency
- Neurological side effects
- Analyzer Issues
Precipitated out upon heating to 50-60°C and redissolved upon further heating to 90-100°C
Bence-Jones proteins
Motion of a liquid when a voltage is applied between the ends of an insulating tube that contains that liquid
electroosmosis
methodologies used to ID protein levels and M spikes
- Electrophoresis (SPEP or UPEP)
- Immunotyping (IT)
- Immunofixation electrophoresis (IFE)
principle of IT
Disappearance of the abnormality in the antiserum-treated pattern indicates the presence of a monoclonal protein.
used to type any suspected monoclonal component previously detected by serum protein electrophoresis
Immunofixation Electrophoresis (IFE)
IEF techniques are similar to electrophoresis except that the separating molecules migrate through a pH gradient.
isoelectric focusing
(not done anymore)
—— is the most common cause of β-γ bridging.
cirrhosis
Excessive loss of serum proteins into the GI tract
protein losing enteropathy (PLE)
Results in hypoalbuminemia → poor surgical outcomes → risk of death
PLE
Fecal excretion of alpha 1-antitrypsin
PLE
↓ albumin
↑ 𝛼2
↑ 𝛾
chronic inflammation
↓ albumin
↑ 𝛼2
variably ↑ β
↓ 𝛾
nephrotic syndrome
↓ albumin
↑ 𝛾
briding
hepatic cirrhosis
↓ 𝛾
hypogammaglobulinemia
↓ albumin
↑ 𝛼2
↓ 𝛾
protein-losing enteropathy
↓ albumin
↑ 𝛼1
↑ 𝛼2
acute inflammation
↓ albumin
↑↑ 𝛾 spike
monoclonal gammopathy
