Biochemistry Lecture 13 PDF

Biochemistry LECTURE (13) DR. El-Sawy 1  Biochemistry Protein Folding  Physical and dynamic p...

Biochemistry LECTURE (13) DR. El-Sawy 1  Biochemistry Protein Folding  Physical and dynamic process by which a polypeptide is folded into a 3-dimensional Def conformation which is necessary for proper protein function.  Spontaneous: aided by the hydrophobic interactions. Hydrophobic amino acids are buried deep inside a protein structure to avoid unstable interactions. Mechanism Hydrophobic interactions aids in keeping protein stable and biologically active by allowing the protein to reduce its surface area.  Chaperones (Heat shock protein): whose function is to assist in this process.  Production of protein structures to perform specific functions. Importance  Prevent protein aggregation. DR. El-Sawy 1  Biochemistry Protein Folding  The molecular protein which: Def Assists in proper protein folding. Prevents them from aggregating.  Chaperones interact with partially folded or improperly folded polypeptides. Importance  Facilitating correct folding pathways.  Molecular chaperones: Hsp 70 family of proteins. Types  Chaperonins: GroEL /Hsp 60 family of proteins. Hsp stands for heat shock protein. DR. El-Sawy 2  Biochemistry Protein Folding 1. Spontaneous. 2. Gene mutation→ an altered protein. Causes 3. Some proteins after abnormal proteolytic cleavage, leads to formation of long fibrillar protein assemblies consisting of β pleated sheets (its accumulation → Amyloidosis). 1. Accumulation of insoluble aggregates of misfolded protein. Effects 2. Degraded by cellular mechanisms. disease Deposit of Alzheimer’s Amyloid beta and tau. Parkinson’s Alpha synuclein. Diseases Type II diabetes Amylin. DR. El-Sawy 3  Biochemistry Protein Folding  Disruption of the secondary, tertiary, and quaternary structure of a protein molecule due to Def cleavage of non-covalent bonds (week bonds).  The primary structure is not affected i.e. peptide bond is not affected. Physical agents Chemical agents Agents 1. Heat. 4. High pressure. 1. Strong acids. 3. Organic solvents. 2. UV light. 5. Violent shaking. 2. Strong alkalies. 4. Heavy metal salts. 3. Ultrasound. 1. Medical supplies & instruments: Sterilized by heating to denature proteins in bacteria → destroy bacteria. Applications 2. Acid gastric juices: cause the denaturation of protein. 3. Alcohol solution 70% : Used as a disinfectant on the skin & This concentration of alcohol is able to penetrate the bacterial cell wall and denature the proteins and enzymes inside of the cell. Biological Chemical 1. Loss of activity. 1. Unfolding of protein molecule. Results 2. Loss of antigen antibody reaction. 2. Destruction of some subsidiary hydrogen bonds. 3. Easily digested. 3. Exposure of some groups as (SH) of cysteine. DR. El-Sawy 4