Molecular Protein Structure Flashcards
How are motifs and domains formed?
Simple secondary structures combine to form structural motifs or larger functional domains
What is a Protein sequence motif?
A protein sequence motif is a pattern of amino acids found in related genes or proteins
Where can motifs and domains be identified within a proteins structure?
Motifs and Domains are independent orders of structure identified within overall tertiary structures
- found and conserved in functionally related proteins
Define what is meant by a motif?
Combination of 2 or more secondary structures to form a recognisable folded arrangement
What is the function of the greek key motif?
Associated with the formation of Β amyloid aggregates and fibrils in alzheimers
Describe what a domain is in molecular terms
Complex structure at tertiary or Quaternary level often involving interactions between distant parts of
proteins or motifs
Explain the structure of Parallel Β sheet motifs
Parallel strands of a Β sheet interlinked with an ɒ helix
=> forming an Β-ɒ-Β motif
How do α helices specifically bind to DNA?
Bind to major groove in DNA
- amino acid sequence of a DNA Binding motif provides specificity
- different DNA binding domains and motifs present the binding helix using different arrangements of the structural motif
Define domain
Functional protein folding units found across different genes and phyla
Describe the structure of beta barrels
Β sheets twisted around forming a closed circular structure
Define what a dimer is
An oligomer consisting of two monomers joined by (strong/weak, covalent/intermolecular) bonds
Describe the domains present in Phospholipase C
4 different recognisable domains present
- each is found individually in other proteins
What are DNA Binding motifs?
Independently folded proteins containing at least one structural motif that can recognise single/double stranded DNA
What is the function of beta barrels?
Acts as transporters for ions and small molecules
How do the domains present in haemoglobin show evolutionary characteristics from myoglobin?
Each chain if haemoglobin has a tertiary structure similar to the single chain of myoglobin
How do motifs bind to the major groove in DNA?
α helices or β sheets are inserted into the major grooves in a sequence specific manner
Where are motifs found?
Many different protein motifs exist in unrelated proteins that share functional properties
Name some examples of motifs in the body
- Calmodulin
- Greek Key Motif
- Beta Barrel
- Parallel Beta Sheets
Why do motifs bind to the DNA helix major groove?
The major groove contains sufficient information to distinguish one DNA sequence form any other
Describe the structural properties of a domain
- typically larger
- can be contiguous segments
- functional units
- modular in nature
Explain what the Helix turn Helix consists of
2 short helices perpendicular to one another, connected by a turn
What is the result of domain shuffling?
Causes modular units of function being conserved but shuffled between genes
What is the role of the EF hand motifs?
Allow the binding of Ca2+ for myosin light chain
Describe the structure of the Helix Loop Helix motif
Exists as a homo- and heterodimers
Central part made up of overlapping helices - form structure enabling dimerisation
Terminal ends of lower opposing helices contain basic amino acids - interact with DNA major groove
