Modular structure of protein Flashcards
What do simple secondary structures fold into?
Simple secondary structures fold combine to form structural motifs or larger functional domains
What are motifs and domains in terms of structure?
Independent order of structure
Where are motifs commonly found?
Commonly found and conserved across functionally related proteins
What are motifs?
Combination of two or more secondary structures to form a recognisable folded arrangement
What are motifs organised or combined into?
Organised or combined into larger structural and functional domains
What is the EF hand and what does it resemble?
Is a motif which allows the binding of Ca2+ and resembles a helix turn
What does the greek key motif consist of?
Consists of antiparallel beta strands
Why are greek key motifs common?
Form easily during protein folding process and therefore common and isn’t associated with a specific function
What happens in a beta barrel?
Beta strands wrap around to form circular tunnel
What is a domain?
Complex structure at the tertiary or quaternary level often involving interactions between distant parts of a protein or motifs
What does each chain of HB have a similar structure to and what does this suggest?
• Each chain of HB has a very similar tertiary structure to a single myoglobin chain
○ This strongly suggests evolution from a common ancestral O2 binding polypeptide
What are the 4 types of DNA binding motifs?
Helix loop helix
Leucine Zipper
Helix turn helix
Zinc finger
What provides specificity to DNA binding motifs?
Amino acid sequence of a DNA binding motif provides specificity
Where is a Helix loop helix(DNA binding motif) found?
Found in some transcription factors
What is the central portion of a helix loop helix made from?
Central portion made from overlapping helices that form a structure enabling dimerization
What does the larger helix of the helix loop helix contain?
Contains the DNA binding regions
What does the terminal part of the lower opposing helices contain and do?
Terminal part of the lower opposing helices contain basic amino acids that interact with the major groove of the DNA- giving rise to b/HLH functional domain
What are Leucine zippers formed from?
Formed from 2 contiguous alpha helices and is a dimeric protein formed from 2 polypeptide chains
What do dimers do in leucine zippers?
Dimers zip together in the top stalk to form a short coiled coil
How is the coil held together in leucine zipper?
Coil held together by hydrophobic interactions down opposing sides of the helix
What does heterodimerization do?
Expands the regulatory potential of leucine zippers
What is a helix turn helix?
Two short helices orientated at right angles to each other and connected by a turn
Where is helix turn helix found?
This Motif is found in both eukaryotic and prokaryotic DNA binding proteins
What is CRO?
A homodimer
What does CRO recognise?
Recognises palindromic sequence and by binding DNA represses transcription
What only interacts?
Only recognition helix interacts with nucleotide sequence and locates within the major groove
What is a zinc finger?
Alpha helix and beta sheet held together by non-covalent interactions with zinc
Where is zinc fingers present?
Present in many hormone receptors
What does the alpha helix of each motif interact with?
Alpha helix of each motif interacts with the major groove of DNA and recognises a specific DNA sequence
