Four levels of protein Structure

Transcription

1 Proteins (polypeptides) Four levels of protein Structure Primary Structure (1 structure): Secondary Structure (2 structure): Tertiary Structure (3 structure): Quaternary Structure (4 structure):

2 Proteins (polypeptides) Four levels of protein Structure 1 structure 2 structure Alpha-helix Beta pleated sheet

3 Proteins (polypeptides) Four levels of protein Structure 3 structure

4 Proteins (polypeptides) Four levels of protein Structure 4 structure

5 One mistake in primary structure : Lecture 3 Normal RBC RBC from sickle cell patient

6 Proteins and their environment Cellular environment is important for protein conformation (3D structure) and thus protein function 3D structure of proteins is held together by non-covalent bonds Proteins can therefore be denatured Chaperone proteins help proteins fold (see figure 5.23 Campbell)

7 Proteins are agents of molecular specificity! R group (20 different side chains) There is an R-group to transact any chemical reactions!!! Need a positive charge Need a negative charge Need a H-Bond Need a hydrophobic partner etc. Proteins can have a net charge: typically dictated by R-group at physiological ph. Consider Tyr-Asp-Val at ph 7

8 Proteins are agents of molecular specificity! Glucose Galactose RECOGNITION and the ability to BIND SPECIFIC MOLECULAR STRUCTURES is central to protein function!! Small molecule recognition Large molecule recognition

9 Proteins are agents of molecular specificity! Use of small molecule recognition Sugar molecule Sugar binding site Ex. Lectins are proteins that bind specific sugars Place 1 Place 2 By ligand

10 Proteins are agents of molecular specificity! Use of small molecule recognition outside cell Inside cell antibody invader Antibodies are large groups of proteins that recognize small molecular signals on invading organisms, etc.

11 Proteins are agents of molecular specificity! Use of small molecule recognition toxin Many toxins are proteins that can find Target cells through binding to small molecular signals on the Target cells cell outside cell A way for signals and information to be sent and received between cells. Inside cell

12 Proteins are agents of molecular specificity! Big molecule recognition Protein Protein interaction Cell recognition Structural proteins Protein receptors (e.g. insulin, endorphins) Specificity in Membrane Dynamics (e.g. endosomes, Golgi, etc) protein marker wrong place membrane compartment right place wrong place right place wrong place right place

13 Proteins are agents of molecular specificity! How is Recognition Accomplished? By providing a Binding Site that favors the Molecular Target being detected above all others. Target Molecule

14 Proteins are agents of molecular specificity! Ex. Sucrase - and enzyme the cleaves sucrose into glucose and fructose What helps sucrase recognize and bind to sucrose? 3D shape form a binding site Enzyme cycle for Sucrase Functional groups help stabilize interactions noncovalent interactions Does sucrase prefer to bind sucrose - or glucose and fructose?????

15 Nucleic Acids An information storage macromolecule polymer of nucleotides linked by phosphodiester bonds Function: 2 Types: Information Storage molecule Store Energy (ATP) DNA deoxyribonucleic acid Permanent blueprint for specifying proteins Makes up our genes, seen as chromosomes in the nucleus RNA ribonucleic acid mrna temporary blueprint of information for specifying proteins trna transfer RNA rrna ribosomal RNA Both DNA and RNA are involved in protein synthesis! Central Dogma:

16 Nucleic Acids An information storage macromolecule 3 parts to a nucleotide (monomer of nucleic acids) Ribose (RNA) or deoxyribose (DNA) Phosphate Base: DNA RNA Adenine Guanine Thymine Cytosine (A) (G) (T) (C) Adenine Guanine Uracil Cytosine (A) (G) (U) (C)

17 Nucleic Acids An information storage macromolecule C1 is attached to base Purines A and G (2 rings) Pyrimidines C, T, and U (1 ring) C2 is missing OH in DNA C3 is reactive site (3 end or 3 OH) C5 attached to phosphate: reactive (5 end or 5 phosphate) Base u

18 Nucleic Acids An information storage macromolecule Polymer of nucleotides linked by phosphodiester bonds