protein cleavage - week 2 Flashcards
what is protein cleavage ?
the process by which specific peptide bonds between amino acid residues are hydrolysed
What performs the leakage of peptide bonds?
proteins known as proteases
Why is protein cleavage important?
- protein degradation
. recycling, digestion - post-translational porcessing
. N-terminal met, signal sequences. precursors
Proteins fall into broad families that share common characteristics. name examples
- metalloproteases eg. carboxypeptidase A
- Serine proteases eg. Chymotrypsin
- Aspartyl proteases eg. HIV protease
What is CPA 1 and where is it found?
- digestive enzyme found in the gut
Describe CPA 1
- member of the family of proteins called metalloprpteases
- contains zinc
What do all metalloproteases have?
metal ion in active site of enzyme
What does CPA do?
- cleaves off last C-terminal residues form peptide chain
- functions best when residue Is aliphatic (val, leu, ill, ala)
where is chymotrypsin found?
digestive enzyme in the gut
What family is chymotrypsin a member of?
serine protease
what do all serine proteases have?
a critical serine residue in active site
What does chymotrypsin do?
cleaves peptide bond on the carboxyl side of aromatic or large hydrophobic residues
What is the role of HIV protease?
- cleave itself out of a large polypeptide chain produced from oral genetic material
- proceed to chop up remaining bits of polypeptide into functional proteins
- viral réplication
What family is HIV protease a member of?
aspartyl protease
What does HIV protease have in its active site?
critical aspartic acid
name examples of proteins synthesised in linger form than active chain and require cleavage
- transit peptides
- longer chain assists in folding pf protein
- longer chain renders the protein inactive
How do many gastric proteases synthesise?
in pro-form (zymogens)
What doe preproteins and proproteins require?
need to be cleaved by other proteases into active from
Give an example of pro forms
- carboxypeptidase S and Chymotrypsin initially synthesised as zymogens
- both cleaved any site-specific protease trypsin into active form
What is a pre-protein?
- protein precursor that contains a single peptide sequence
- nonpolar sequence at the head of the growing polypeptide chain and required for its transfer into cistern of the ER, signal sequence then cleaved to form protein or pro protein
What are pro-proteins?
any protein cleaved by converts to form a smaller protein or biologically-active polypeptide
