Lecture 1: Proteins PDF

Proteins Lecture 1  Topics to be covered: Processes involved in protein metabolism Classes of proteins Protein determination Causes of protein variation pathologically or analytically  Most proteins are metabolized in ______________ Basic unit ______________ linked tog...

Proteins Lecture 1  Topics to be covered: Processes involved in protein metabolism Classes of proteins Protein determination Causes of protein variation pathologically or analytically  Most proteins are metabolized in ______________ Basic unit ______________ linked together by ______________ to make proteins Protein breakdown in the body produces ____________and ___________; urea produced in ___________ and eliminated in _____________ Protein The word protein comes from Greek “prota” meaning “of primary importance” Named by the Swedish chemist Jons Berzelius in 1838. First protein to be sequenced was insulin by Frederick Sanger in 1958 Protein Synthesis and Degradation Synthesis 1 Involves Transcription (DNA to mRNA) and Translation (mRNA to Protein). Folding 2 Polypeptides fold into functional proteins with the help of chaperones. Degradation 3 Ubiquitin-Proteasome system tags and degrades damaged proteins. Central dogma  The size of synthesized protein can be determined by the number of AAs it has and by its total molecular weight. Largest known proteins are the _________ a component of the muscle. Peptide synthesis which rely on organic synthesis techniques such as chemical ligation to produce peptides in large scale  Protein Structure Proteins are not rigid molecules rather they are folded into unique 3- dimentional structures. Proteins are classified into three main classes: I. Globular proteins (soluble) a. Albumin b. Globulins c. Protamines and Histones II. Fibrous Proteins (structural) a. Keratins b. Collagen III. Membrane proteins (receptors) Structure determination Common experimental methods of structure determination include: 1. X-ray crystallization 2. NMR spectroscopy Both of which can produce information at atomic resolution  Electrophoresis method for analyzing plasma protein Common method of analyzing plasma proteins Principle……. The amount of these five bands can be conveniently quantified using densiometric scanning machine Conversion of these bands to characteristic peaks of albumin, alpha1 globulin, alpha2 globulin, beta globulin and gamma globulin. These bands concentration/number change in many diseases. The traditional method for measuring total protein uses the biuret reagent, ________________,_________________ Serum protein electrophoresis agarose gel Serum proteins are separated into 6 groups: Albumin α1 - globulins α2 - globulins β1 - globulins Are seen as β2 - globulins almost one band γ - globulins Figure is found at http://www.sebia-usa.com/products/proteinBeta.html# This serum protein electrophoresis demonstrates a normal pattern, with the largest peak for albumin. Albumin is the most abundant circulating plasma protein (40–60 % of the total) Playing important roles in the: maintenance of the colloid osmotic pressure of the blood, in transport of various ions, acids, and hormones. It is a globular protein with a molecular weight of approximately 66,000 D. It has a relatively low content of tryptophan and is an anion at pH 7.4 Plasma proteins Proteins are involved in so many bodily functions hence much clinical information could be obtained by examining and measuring them together with the relative ease of assaying them, makes their determination a valuable diagnostic tool as well as a way to monitor clinical progress. Variations in plasma protein concentrations can be due to any of three changes: in the rate of protein synthesis, the rate of removal, and in the volume of distribution. Protein Disorders: Types Causes Genetic mutations Cystic fibrosis, sickle cell anemia, Huntington’s disease Environmental toxins Disrupt protein metabolism Aging Disrupt protein metabolism Malnutrition Disrupt protein metabolism Total Protein = Plasma proteins = Serum protein Increase in total protein (_________________) may be due to: Haemoconcentration as a result of dehydration (vomiting, diarrhea, burns) Poor kidney function Acute and Chronic infections Acute liver disease Multiple myeloma and other malignant tumors  Decrease in total protein (hypoproteinaemia) may due to: Decreased formation of protein in liver Insufficient protein intake Sever hemorrhage Loss of protein in urine Severe liver disease Malabsorption Dilution of blood by excessive IV administration of glucose in water or saline Pre-analytical Plasma proteins could be affected by posture: 10-20% increase occurs within 30 minutes of becoming upright after a period of recumbency. Prolonged tourniquet application can rise a significant protein concentration. In both cases, the change in protein concentration is caused by increased diffusion of fluid from the vascular into the interstitial compartment.