BB4 Protein Modification

Question 0

Forms of modification

Answer 0

• acetylation
• hydroxylation
• glycosylation
• phosphorylation

Question 1

Protein modification

Answer 1

• the modification of selected residues in a polypeptide

* not as a component as synthesis

Question 2

Acetylation

Answer 2

• modifies N-terminal amino acid
• involves Acetyl CoA
• only eukaryotes, not prokaryotes
• not in mito or chloro
• stops other proteins from breaking that protein apart

Question 3

Hydroxylation

Answer 3

• addition of an OH group to the side chain of specific amino acids in a protein

Question 4

Amino acids involved in hydroxylation

Answer 4

• proline

* lysine

Question 5

Essential component of collagen

Answer 5

• hydroxyproline
• hydrogen bonding within the collagen fiber
• structural stability

Question 6

Repeating unit in collagen

Answer 6

Gly—Xaa—Yaa

• 4-Hyp only in 3rd position

Question 7

4-Hyp

Answer 7

• formed by enzyme prolyl hydroxylase

* requires ascorbic acid / vitamin c

Question 8

Glycolysation

Answer 8

• the attachment of sugar molecules to specific amino acids in a polypeptide chain
• only eukaryotes, not prokaryotes

Question 9

2 forms of glycolysation

Answer 9

• N-Glycolysation

* O-Glycolysation

Question 10

N-Glycolysation

Answer 10

• sugars attached to the NITROGEN in Asparagine (N)

Question 11

N-Glycolysation sequence

Answer 11

Asn—Xaa—Ser or Asn—Xaa—Thr

•Xaa not proline

Question 12

O-Glycolysation

Answer 12

sugars are attached to the OXYGEN in the side chain of the amino acids
• Serine
• Threonine
•no characteristic sequence pattern

Question 13

Phosphorylation

Answer 13

• attachment of a phosphoryl group to the side chains of specific amino acids in a protein
• most common

Question 14

Phosphorylation occurs on the side chain OXYGEN atoms of

Answer 14

• Threonine
• Serine
• Tyrosine

Question 15

Phosphoryl attached to amino acid by enzyme…

Answer 15

protein kinase

Question 16

Phosphoryl removed from amino acid by enzyme…

Answer 16

protein phosphatases

Question 17

Cleaving of peptide bonds performed by proteins…

Answer 17

proteases

make-break-recycle to make new

Question 18

Types of proteases

Answer 18

• Carboxypeptidase A
• Chymotrypsin
• HIV Protease
all active site dependent

Question 19

Carboxypeptidase (function)

Answer 19

cleaves off the last C-Terminal residue from a polypeptide chain
• works best with aromatic or bulky aliphatic residue

Question 20

Carboxypeptidase A is a member of the

Answer 20

• metalloproteases

* metal ion at active site - zinc

Question 21

Chymotrypsin (function)

Answer 21

cleaves peptide bonds on the carboxyl side of aromatic or large hydrophobic residues
• find hydrophobic areas when protein being broken up anyway

Question 22

Chymotrypsin is a member of the

Answer 22

•Serine Protease family

Question 23

HIV protease is a member of the…

Answer 23

• Aspartic Protease family

* 2 aspartate residues central to the active site

Question 24

HIV protease (function)

Answer 24

* cleave itself out of chain protein (from genetic material of virus) * then cleaves out remaining proteins of the virus * critical to viral replication, HIV protease inhibitors

Question 25

Reason why proteins are synthesized as longer chains than native chain

Answer 25

* added sequence directs a protein to specific compartments within a cell * longer chains assists folding correctly * longer chain renders protein inactive

Question 26

Protein Kinase A recognizes

Answer 26

Arg-Arg-small-Ser-Large hydrophobic Arg-Arg-small-Thr-Large hydrophobic