Modular structure of proteins Flashcards
What is a motif in a protein? [2 marks]
The minimum arrangement of independently forming secondary structures combining recognisable folds across many proteins
OR
A combination of two or more secondary structures to form a recognisable folded arrangements.
What do motifs usually associate with? [1 mark]
Domains with functional properties.
What are examples of well known domains? [3 marks]
- Immunoglobin: two anti-parallel beta sheets.
- ATPase: found in many different enzymes.
- Transmembrane: formed form multiple hydrophobic alpha helices connected by intervening hydrophilic loops.
What is the function and structure of the EF hand and where is it found? [3 marks]
- Binds to Ca2+.
- Resembles a helix turn helix but combines with a metal ion like calcium.
- Found in calmodulin & troponin-C.
What is the function and structure of the Greek key? [2 marks]
- It isn’t associated with a specific function.
- Consists of antiparallel beta strands.
What is the structure of a beta barrel? [2 mark]
- Bea strands wrapped around.
- Forms a circular tunnel.
What is the structure of a beta-alpha-beta? [1 mark]
Parallel strand of a beta sheet interlinked with alpha helix.
Where do helices on DNA binding motifs go? [1 mark]
Into the major groove of DNA.
Where is the helix loop helix found? [2 marks]
- Max & Mad
- Ca2+ binding
Where is the helix turn helix found? [3 marks]
- Cro
- Tryptophan
- Ca2+ binding
Where is the leucine zipper found? [1 mark]
GCN4 (involved in translation in yeast)
Where is the zinc finger found? [1 mark]
Hormone receptors.
Structure of membrane bound receptors [3 marks]
- Intracellular region: responsible for downstream signalling and functionality of the protein.
- Transmembrane region: embedded in lipid bilayer, formed from bundles of helices (alpha helices are around 20 a.a. long)
- Extracellular region: main structure of protein.
What is domain shuffling? [1 mark]
When modular units of structure are conserved but shuffled between genes.
Structure of helix loop helix [4 marks]
- Binds only in dimeric form.
- Exist as hetero and homodimers.
- Central part is from overlapping helices to allow dimerisation.
- Terminal part of lower opposing helices contains basic amino acids that interact with major grooves of DNA.
