B1.2 HL Protein structure.pptx.pdf

Different properties of the R-groups Non-polar & hydrophobic Polar & hydrophilic Polar or...

Different properties of the R-groups Non-polar & hydrophobic Polar & hydrophilic Polar or charged & hydrophilic 1st level of protein structure The sequence of aa in the protein make up its primary structure The combination of R-groups with specific properties ultimately determines the 3D-structure of a protein 2nd level of protein structure Hydrogen bonds between different peptide bonds within the chain generate a secondary structure Secondary structures commonly fold the chain into helical or sheet-like structures 3rd level of protein structure Interactions between R-groups determine the final 3D shape – the protein’s tertiary structure H-bonds, ionic bonds, hydrophobic interactions Disulfide bridges between the R-groups of two cystein aa – the only covalent bond that shapes the 3D-structure! Protein structure and environment interactions Interactions with the its environment modify the shape of the protein Protein structure and environment interactions Ex: Integral membrane proteins Polar or charged aa facing the aqeous outside and inside of the membrane Non-polar aa facing the lipid membrane interior 4th level of protein structure Some proteins consists of more than one polypeptide chain Assembly of interacting chains gives the protein a quaternary structure Ex: insulin (2 subunits), collagen (3 subunits), haemoglobin (4 subunits) Levels of protein structure - summary The 3D-structure of a protein depends on interactions within the polypeptide chain and interactions with its environment Primary Secondary Tertiary Quaternary Video on protein structure Conjugated proteins The function of some proteins depends on other, non-peptide groups being attached to the polypeptide These groups are called prosthetic groups Prosthetic groups could be metal ions, lipids or sugars Ex: the prosthetic group of hemoglobin is an organic ”heme” molecule containing Fe2+ ions that bind oxygen General protein shapes Most proteins fold into either fibrous or globular 3D structures Insulin – a non-conjugated Collagen – a non-conjugated protein with a quartenary protein with a quartenary structure and an overall structure and an overall globular shape fibrous shape