Protein Structure Flashcards
What is the primary structure?
The sequence of amino acids
What kind of bond is present between amino acids?
Peptide bond
During a condensation reaction, what molecule is released?
H2O
What is the secondary structure?
Folding of polypeptide chains. Determined by primary structure due to polar and non-polar side chain interactions
What different shapes are present in secondary structure?
α-helix: H bonding within chain
ß-sheet: interchain H bonds, either parallel or antiparallel
random coil: in-between helix and sheet
What is the tertiary structure?
The 3D structure of a protein. The way in which individual secondary elements pack together within a protein
What does a common structure indicate?
A common function
Why do some proteins have multiple domains?
Multiple complex cellular functions
What is the quaternary structure?
Interactions between individual proteins in a multimeric complex
Examples of protein modification
glycosylation, phosphorylation, lipid modification, proteolysis, disulphide bridges
Disulphide bridges form between…
Cysteine amino acids in proteins
What kind of proteins is glycosylation mainly used on?
Extracellular proteins
What are lipid modifications in proteins used for?
Binding proteins to membranes
Protein phosphorylation/dephosphorylation is mainly used for…
Regulation. Switching on/off
4 structural types of transmembrane proteins
Single-pass, multi-pass, ß-barrel, amphipathic helix
Single pass type 1 membrane protein?
Protein spanning the membrane once, with its N-terminus on the extracellular side of the membrane and removal of its signal sequence - E.g. T cell surface glycoproteins
Single pass type 2 membrane protein?
Protein spanning the membrane once, with its N-terminus on the cytoplasmic side of the membrane - Transmembrane domain located close to N-terminus and it functions as an anchor - E.g. Tumor Necrosis Factor
Difference between N-terminus on single pass type 1 and 2 membrane proteins
Type 1 has its N-termins on the extracellular side
Type 2 has its N-termins in the cytoplasmic side
What is the N-terminus?
Refers to the start of an amino acid chain. The free amine group -NH2
What is the C-terminus?
Refers to the end of a polypeptide chain. The free carboxyl group - COOH
What type of lipid modifications bind proteins to cytosolic side of membrane?
Acylation
2 types of glycosylation modifications?
- N-linked attachment via asparagine - O-linked attachment via hydroxyl group of serine/threonine
What forms the basis of blood groups?
Glycosylation
What do kinases do?
Phosphorylates
What do phosphatases do?
Dephosphorylates
