University:
Amherst College
Course:
BIOL 330 | Biochemical Principles of Life at the Molecular Level
Academic year:

2011
Views:

482

Pages:

28
Author:

Frankie Mays

Protein Structure What do proteins do? • Chemistry – Metabolism – Factories of cellular components (FaDy acid synthase) • Transport – Oxygen in blood (hemoglobin) – Signals from outside cells (nervous system) • Structure – Internal scaﬀolding in cells (acMn) – Hair and nails (collagen) • Movement – Myosin (animal muscles) – Flagella and Cilia (cellular propulsion) How do proteins work? • Biological Nano Machines • Highly complex • But… based on fundamentals of chemistry Understanding Protein Structure 1. Primary structure 2. Secondary structure 3. TerMary Structure Sequence leads to structure Primary Structure -‐ Sequence • Amino-‐acid side chains along the PepMde Backbone • Covalent bonds making a string • Proteins have many “residues” – Proteins can be 100-‐1000s of residues – 20 regular amino acids Side chains come in 4 “ﬂavors” The Backbone Proteins are long stretches of amino acids 9 amino acids, 20 possible = How many unique sequences? Understanding Protein Structure 1. Primary structure 2. Secondary structure 3. TerMary Structure Secondary Structure • Proteins have unique structures – i.e. not like random mess of string • Final structure is an assembly of secondary structure elements • Backbone carbonyl and amide-‐proton hydrogen bonding are key! Basic forms of Secondary Structure • Random Coil • Alpha-‐Helix – α-‐helix • Beta-‐sheet – β-‐sheet • Loops Basic forms of Secondary Structure • Random Coil • Alpha-‐Helix – α-‐helix • Beta-‐sheet – β-‐sheet • Loops Alpha Helices Two important helical notes Beta Sheets Beta sheets can assemble diﬀerent ways Loops • Connect helices and sheets • Are o`en structured, but can be very ﬂexible. • Glycine o`en present in loops • MathemaMca Again TerMary Structure • The assembly of secondary structure • Side chains and backbone interacMons determine how the secondary structure elements align • Non-‐covalent bonding primary stabilizaMon • Only mildly stable, can be broken up by heaMng or using chemical denaturants Side Chain Residues Come in 4 “ﬂavors” Non-‐covalent interacMons hold it together Protein’s “hide” their hydrophobic core Disulphide Bonds RelaMve strength of Bonds The folded state is the “lowest energy” state TerMary Structure • The assembly of secondary structure • Side chains and backbone interacMons determine how the secondary structure elements align • Non-‐covalent bonding primary stabilizaMon • Only mildly stable, can be broken up by heaMng or using chemical denaturants TerMary Structure From Noodles to Nanomachines

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