Protein Motifs Flashcards
What is a protein motif
Arrangements of limited numbers of secondary structure elements
Form part of larger regions of proteins-domains
In multi-domain proteins each domain has a role
What are ß-α-ß motifs
Found in almost every structure that contains parallel b-sheet
a-helix connects the C-terminus of one b-strand with the N-terminus of a second
b-a-b contains two b-strands, two loop regions and one a-helix.
Can be found in larger, repeating domains
Found in repeating units in proteins
What are some different types of protein motifs
Helix-loop-helix
Zinc finger
EF hand motif
Greek key motif
b-a-b motif
Leucine rich motif
Rossman fold
What is y- crystallin
Y-crystallin protein is in lens of the eye
Responsible in part for transparency and refractive power
Contains 2 domains
Each domain contains two Greek key motifs
what is the structure of a pyruvate uinase
530 amino acids
Tetramer, only a monomer is shown
4 different domains
N-terminal domain key in oligomer formation
a/b barrel is core functional domain
Why are proteins multi domain
One suggestion is that it makes evolving new proteins easier- Easier than single point mutations
A domain in one protein can be transposed to another protein-should do the same job
Multidomain organisation makes it easy to introduce control and regulation
Multidomain construction simplifies folding and assembly
Stabilizes the protein
Large single domain protein would take a long time to fold
Domains fold independently
What can domains be
Domains can be a-helical, b-strand or a mixture of both.
Why are oligomers important
Important for function
Stabilises proteins
Cooperativity
What are the characteristics of protein motifs
What is a helix-loop-helix motif
What do transcription factors do
What is the zinc finger domain
What is a 4 helix bundle motif
What are the 2 different ways for a 4 helix bundle to be arranged
What is the EF hand motif
What is a Greek key motif
How can motifs be identified
Can be identified by sequencing primary structure
Sequencing a motif can allow identification of other EF hand hoop motifs in the absence of structure
Why are motifs important
They’re important for fold and function
Proteins with similar functions will contain the same motif
What is the problem with a protein having a large loop
Less stability
Why are there many glycine residues in active site regions of proteins
It makes the active site more flexible
how do you compare the structure of two domains
Superposition allows comparisons of different domains ( overlaying the structures in 3D/ putting them ontop of each other)
Root mean square deviation- gives a quantitative measure of how similar the two protein structures are
What are domains in proteins
Domains are combined to make proteins
