SOME PROMINENT FUNCTIONS OF PROTEINS

Presented as a part of Protein structure course (Comp. Bio.) at IMSc

Transcript

1. Vinay Vaibhav The Institute of Mathematical Sciences November 02, 2017 SOME PROMINENT FUNCTIONS OF PROTEINS
2. Nature Reviews Neuroscience 14, 161-176 (March 2013) https://www.nature.com/scitable/topicpage/mitosis-14046258 http://www.sigmaaldrich.com/life-science/metabolomics/enzyme- explorer/learning-center/structural-proteins/tubulin.html ➤ Three dimensional structures determine their functions ➤ Proteins can have many functional descriptions at several different levels Tubulin An enzyme that hydrolyses GTP Structural protein: Polymerizes to form a tube like structure Forms a network of microtubules growing out of centrosome In cell division it forms the mitotic spindle In certain motile eukaryotes, forms cilia and flagella
3. https://en.wikipedia.org/wiki/Electron_transport_chain http://juohco.com/reason-why-liver-health-is-important-to-your-fertility/ ➤ Virtually involved in all biological life processes - Catalysis of Metabolic Processes - Energy Transfer - Gene Expression - Cellular Communication - Defence - Transport of Solutes across Biological Membranes - Forming Intracellular and Extracellular Structures - Cell/Tissue-Specific Functions https://www.nature.com/scitable/ebooks/cell-biology-for- seminars-14760004/122995633#bookContentViewAreaDivID
4. OUTLINE ➤ Information Transfer Process in Cell ➤ Structural Supports for Cells ➤ Proteins in Plasma Membrane ➤ Defence System
5. Information Transfer Process in Cell Image: https://www.nature.com/scitable/ebooks/cell-biology-for-seminars-14760004/122995379#bookContentViewAreaDivID ➤ Chromatin: A condensed complex formed by DNA with some protein called histone that is organised into subunits called nucleosomes ➤ Chromatin fold specifically to form chromosome ➤ Transcription: Enzymes called RNA polymerase build RNA (mRNA) molecules that are complementary to a portion of one strand of the DNA double helix ➤ Translation: After the transcription of DNA to mRNA is complete the reading of these mRNAs to make proteins begins by tRNA ➤ Ribosomal RNA (rRNA) molecules form the core of a cell's ribosomes where protein synthesis takes place ➤ Every amino acid is represented by a three-nucleotide sequence or codon along the mRNA molecule ➤ tRNA are responsible for matching amino acids with the appropriate codons in mRNA
6. Image: https://www.nature.com/scitable/ebooks/cell-biology-for- seminars-14760004/122995379#bookContentViewAreaDivID https://en.wikipedia.org/wiki/Translation_(biology)#/media/File:Protein_translation.gif
7. Structural Supports for Cells ➤ Cytoskeleton: An extensive network of filaments (microtubules, actin filaments, and intermediate filaments) ➤ Microtubules: Tubulin Actin filaments: Actin ➤ Motor proteins move over these filaments to transport organelles ➤ Microtubules form mitotic spindle during cell division ➤ Actin filaments are involved in various forms of cell movement, including cell locomotion and contraction of muscle cells ➤ Intermediate filaments are strong fibers that serve as architectural supports inside cells https://www.nature.com/scitable/ebooks/cell-biology-for- seminars-14760004/122995633#bookContentViewAreaDivID
8. Proteins in Plasma Membrane Ferrying nutrients across membrane Receive chemical signals from outside the cell Translate chemical signal into intracellular action Anchoring the cell in a particular location Proteins contact lipids in the membrane bilayer and patches of hydrophilic amino acids on the surfaces that extend into the water-based cytoplasm Membrane diffusion: Many proteins can move within the plasma membrane https://www.nature.com/scitable/ebooks/cell-biology-for- seminars-14760004/122995633#bookContentViewAreaDivID https://www.nature.com/ scitable/ebooks/cell-biology-for- seminars-14760004/12299563 3#bookContentViewAreaDivID
9. Defence System ➤ Immune system: Highly efficient defence system against pathogens ➤ Antibodies specialise in binding to foreign elements (antigen) - Sometimes binding neutralise foreign elements - For large pathogens, tag them to be swallowed by phagocytes ➤ Complement system: Proteins like antibodies, exist in blood - After binding to pathogens, bind to each other to form a killing complex - Acts as molecular drills and perforates the pathogen membrane ➤ Cytokines: Protein secreted by lymphocytes or other WBC - Act as chemical messenger between immune cells
10. AMPs: Short peptides (10-50) which bind to bio-membranes and induce cellular death AMPs are an integral part of the defence system of many organisms Amphipathic Don’t bind to specific receptor, act directly on lipid bilayer component of membrane Superbugs: Bacterias have become multi drug resistant - Resistance to AMPs is less common Anti-tumor activity of AMPs: Cationic AMPs can target cancer cells, these cells are more negatively charged than mammalian cells, also have relatively larger surface area Anti-Microbial Peptides
12. Thank You