Modular Structure Of Proteins Flashcards
What is a sequence motif?
Pattern of amino acids
Where is motif and domains identities within?
Overall tertiary/quaternary structure
What are motif + domains?
Independent order structure
What is definition of a motif?
Combination of 2 or more secondary structures to form recognisable folded arrangement
What is definition of domain?
Functional unit than motif but both are evolutionarily conserved motifs + modular in nature=> can be found in different proteins that are unrelated
What is a DNA binding motif?
Helixes can be inserted into major groove of DNA in sequence specific manner
What is transcription factor?
Proteins that bind to DNA + regulate transcription
Many different TFs but they each contain small number of conserved to form domain that interact with DNA
Alpha helixes are important in…..
DNA binding
What is helix loop helix motif?
Binds DNA only in dimeric form
Exists as heterodimers (different monomers) and homodimers (identical monomers)
Central portion is made from overlapping helices that form structure allowing dimerisation
Terminal part of lower opposing helices basic amino acids that interact with major groove of DNA => giving rise to b/HLH functional domain
Give an example of helix loop helix motif?
Mad, max, myo, myoD
What is leucine zipper motif?
Formed from contiguous alpha helices
Dimers zip together in top stalk to form short coiled coil
Coil is held together by hydrophobic interactions down opposing sides of the helix
As in b/HLH basic amino acids dominate lower part of helix + interact with DNA major groove
Heterodimerisation expands regulatory potential of leucine zippers
What is helix turn helix motif?
Consists of 2 short helices orientated at right angle to each other + connected by a turn
What is zinc finger motif?
Alpha helix + beta sheets held together by non covalent interactions with zinc
Alpha helix of each motif interacts with major groove of DNA + recognises specific DNA sequence
Give an example of zinc finger motif
Many of hormone receptors such as oestrogen, progesterone receptors etc
