Biomolecules – Protein

Shape matters with proteins Even one wrong amino acid can cause serious damage. In sickle cell anemia, the amino acid sequence in one of the four polypeptide chains (Beta globin - a single chain of 147 amino acids.) is incorrect for 1 amino acid at the 6th position. Normal hemoglobin has a polar amino acid – glutamate whereas sickle cell beta globin has a nonpolar valine. This one amino acid substitution alters the shape of the protein molecule, reducing its ability to carry oxygen. http://web.mit.edu/site/spotlight/3306/ http://www.mhhe.com/biosci/esp/2001_gbio/folder_structure/ge/m5/s1/gem5s1_3.htm

Protein Structure Primary Structure (1o) – the order of the amino acids Secondary Structure (2o) – hydrogen bonding– helices/sheets Tertiary Structure (3o) – weaker IMF – “globs” Quaternary Structure (4o) – association of subunits

Protein Folding Protein Folding

Secondary Structure: Hydrogen Bonds!!!

Protein Roles - TAMES T A M E S Proteins have 5 major roles in living systems. These are transport of other molecules, antibody formation and recognition, metabolic control, enzyme activity and structural support. M E S

Transport Protein - Hemoglobin Hemoglobin is a tetramer composed of 4 globin molecules; 2 alpha globins and 2 beta globins. The alpha globin chain is composed of 141 amino acids and the beta globin chain is composed of 146 amino acids (Perutz, 1978). Both alpha and beta globin proteins share similar secondary and tertiary structures, each with 8 helical segments (labeled helix A-G) (Keates, 2004). Each globin chain also contains one heme molecule. The heme molecule is composed of a porphyrin ring, which contains 4 pyrrole molecules cyclically linked together, and an iron ion ligand bound in the center. Transport Protein - Hemoglobin

Transport channels – a variant on transport molecules a hemolysin from the bacterium Staphylococcus aureus: The protein is assembled from seven chains, which combine when they encounter an appropriate cell surface receptor. The barrel is very hydrophobic, punches through the cell membrane, and allows the indiscriminate flow of ions in and out of the cell, destroying it. http://chemistry.umeche.maine.edu/MAT500/Proteins9.html

Antibody Protein - Immunoglobulin An antibody (Ab), also known as an immunoglobulin (Ig), is a large Y-shape protein produced by plasma cells that is used by the immune system to identify and neutralize foreign objects such as bacteria and viruses. The antibody recognizes a unique part of the foreign target, called an antigen. http://en.wikipedia.org/wiki/Antibody Antibody Protein - Immunoglobulin

Metabolic Control – Growth Hormone The major form of the human growth hormone is a protein of 191 amino acids. The structure includes four helices. Since it is hydrophobic, the molecule cannot pass into the cell by exerts its influence by attaching to “receptors” on the cell surface.

Enzyme - Catalase Catalase is a common enzyme found in nearly all living organisms exposed to oxygen (such as vegetables, fruit or animals). It catalyzes the decomposition of hydrogen peroxide to water and oxygen. It is a very important enzyme in protecting the cell from damage by reactive oxygen. Likewise, catalase has one of the highest turnover numbers of all enzymes; one catalase molecule can convert millions of molecules of hydrogen peroxide to water and oxygen each second. Catalase is a tetramer of four polypeptide chains, each over 500 amino acids long. It contains four porphyrin heme (iron) groups that allow the enzyme to react with the hydrogen peroxide. The optimum pH for human catalase is approximately 7 and has a fairly broad maximum (the rate of reaction does not change appreciably at pHs between 6.8 and 7.5). The pH optimum for other catalases varies between 4 and 11 depending on the species. The optimum temperature also varies by species. http://en.wikipedia.org/wiki/Catalase

Collagen Structure – cell’s skeleton and human body motion and cabling Actin filaments are made of self assembling G actin globular proteins. http://micro.magnet.fsu.edu/cells/microfilaments/microfilaments.html Myosin acts with actin to create sliding/contractile motion. Collagen