protein cleavage - week 2

Question 1

what is protein cleavage ?

Answer 1

the process by which specific peptide bonds between amino acid residues are hydrolysed

Question 2

What performs the leakage of peptide bonds?

Answer 2

proteins known as proteases

Question 3

Why is protein cleavage important?

Answer 3

• protein degradation
  . recycling, digestion
• post-translational porcessing
  . N-terminal met, signal sequences. precursors

Question 4

Proteins fall into broad families that share common characteristics. name examples

Answer 4

• metalloproteases eg. carboxypeptidase A
• Serine proteases eg. Chymotrypsin
• Aspartyl proteases eg. HIV protease

Question 5

What is CPA 1 and where is it found?

Answer 5

• digestive enzyme found in the gut

Question 6

Describe CPA 1

Answer 6

• member of the family of proteins called metalloprpteases
• contains zinc

Question 7

What do all metalloproteases have?

Answer 7

metal ion in active site of enzyme

Question 8

What does CPA do?

Answer 8

• cleaves off last C-terminal residues form peptide chain
• functions best when residue Is aliphatic (val, leu, ill, ala)

Question 9

where is chymotrypsin found?

Answer 9

digestive enzyme in the gut

Question 10

What family is chymotrypsin a member of?

Answer 10

serine protease

Question 11

what do all serine proteases have?

Answer 11

a critical serine residue in active site

Question 12

What does chymotrypsin do?

Answer 12

cleaves peptide bond on the carboxyl side of aromatic or large hydrophobic residues

Question 13

What is the role of HIV protease?

Answer 13

• 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

Question 14

What family is HIV protease a member of?

Answer 14

aspartyl protease

Question 15

What does HIV protease have in its active site?

Answer 15

critical aspartic acid

Question 16

name examples of proteins synthesised in linger form than active chain and require cleavage

Answer 16

• transit peptides
• longer chain assists in folding pf protein
• longer chain renders the protein inactive

Question 17

How do many gastric proteases synthesise?

Answer 17

in pro-form (zymogens)

Question 18

What doe preproteins and proproteins require?

Answer 18

need to be cleaved by other proteases into active from

Question 19

Give an example of pro forms

Answer 19

• carboxypeptidase S and Chymotrypsin initially synthesised as zymogens
• both cleaved any site-specific protease trypsin into active form

Question 20

What is a pre-protein?

Answer 20

• 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

Question 21

What are pro-proteins?

Answer 21

any protein cleaved by converts to form a smaller protein or biologically-active polypeptide