fundamental aspects of primary, secondary, tertiary structure of proteins.
- Primary sequence: the unique sequence of amino acids forming a polypeptide chain
- Secondary structure: produced by twist and turns of the amino acids determined by hydrogen
bonding (alpha helices or beta sheets)
- Tertiary structure: folding of the amino acid chain to make a 3D shape, the conformation
determines the function of the protein (active site is revealed)
- Quaternary structure: (optional) many polypeptide chains fold together to make a protein
definition of native conformation of a protein.
- the most stable conformation of the protein (lower free energy)
- only the native conformation is 100% functional (Anfensen’s dogma - used urea)
- only the primary sequence is required to achieve the native conformation
conditions that cause protein denaturation.
- the use of specific chemical or the addition of heat can cause a protein to lose it structure and
therefore its function (denaturation)
role of thermodynamics in protein folding.
- the proteins native conformation is attained because it is driven by thermodynamics, it is
looking for the most stable conformation (lowest free energy)
mechanisms by which protein cofactors are synthesized.
- a cofactor is a nonprotein chemical component that is bound to a protein (pigments)
- called coenzymes or prosthetic groups
- synthesized through biosynthetic pathways
compartments within cells where proteins are synthesized
- proteins are synthesized (translated) on the ribosomes in the ER or the cytoplasm
- if the protein is destined to remain in the cytoplasm, it will be synthesized on cytoplasmic
ribosomes and will not be transported to the membrane
- if the protein is destined to be secreted or transported to the membrane it will be synthesized
on the ER ribosomes to later undergo protein targeting
mechanism by which proteins are localized to specific intracellular compartments.
- vesicles shuttle the proteins from the ER ribosomes to the golgi, then to the plasma
membrane is it is destined to go there
- a signal peptide on the end of the amino acid is recognized & sent to where it is destined,
signal peptide is the first part that gets translated
- the SRP (signal recognition particle) binds to the signal peptide to recruit the protein complex
to the ER, the ribosome deposits the protein into the ER lumen, then the ribosomes are
released (protein targeting)
- nuclear proteins are imported through pores but they keep their tag because they are
constantly being reimported after the nuclear membrane breaks down during cell division