Transcript CHMI 2227E Biochemistry I

CHMI 2227E
Biochemistry I
Peptides
-General
structure and properties
CHMI 2227 - E.R. Gauthier, Ph.D.
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Peptides
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1
2
2
CHMI 2227 - E.R. Gauthier, Ph.D.
A dipeptide
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Peptides
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Peptides - polarity
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Peptides - nomenclature
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Peptide: hydrolysis
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High Pressure Liquid Chromatography
(HPLC)
PITC = phenylisothiocyanate
PTC = phenylthiocarbamyl
http://www.protein.iastate.edu/aaa.html
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High Pressure Liquid Chromatography
(HPLC)
http://www.protein.iastate.edu/aaa_figure3.html
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Peptide - ionization
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Example of peptides
1. Aspartame: artificial sweetener
COOCH2
O
H3N+-CH-C-NH-CH-C-OCH3
CH2
O
Asp-Phe-methyl ester
2. Oxytocin: stimulates uterine contractions
Disulfide bond
S
S
Cys-Tyr-Ile-Gln-Asn-Cys-Pro-Leu-Gly-NH2
Glycinamide residue: 2HN-CH2-CONH2
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Example of peptides
3.Insulin
Intrachain disulfide bond
Interchain disulfide bonds
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Example of peptides
4.Cystic Fibrosis Transductance Regulator
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General properties of proteins
1. Proteins differ in their Mr.
Mr
(kDa)
Insulin
5.7
Cytochrome c
13
Ribonuclease A
13.7
Lysozyme
13.9
Myoglobin
16.9
Chymotrypsin
21.6
Chymotrypsinogen
22
Hemoglobin
64.5
Serum albumin
68.5
Hexokinase
102
Immunoglobulin G
145
RNA polymerase
450
Apolipoprotein B
513
Glutamate
1,000
dehydrogenase
Protein
#
# chains
residues
51
2
104
1
124
1
129
1
153
1
241
3
245
1
574
4
550
1
800
2
1,320
4
4,100
5
4,536
1
8,300
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Source: Biochemistry. Lehninger.
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Multimeric proteins
Monomer/subunit
1
2
Heterodimer
1
1
Homodimer
Hydrogen bonds:
N-H ----- O-H
N-H ----- N
O-H ----- O=C
N-H ----- O=C
Electrostatic interactions:
COO- ----- H3+N
Hydrophobic interactions:
-CH3 CH3CH3
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Importance of multimeric
proteins – planar cell polarity
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Importance of multimeric
proteins – planar cell polarity
Nature Genetics 38, 21 - 23 (2006)
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General properties of proteins
2. Proteins differ in their pI.
Protein
Pepsin
pI
1
Egg albumin
4.6
Serum albumin
4.9
Urease
5
b-lactoglobulin
5.2
Hemoglobin
6.8
Myoglobin
7
Chymotrypsinogen
9.5
Cytochrome c
10.7
Lysozyme
11
Source: Biochemistry. Lehninger.
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General properties of proteins
3. Frequency of amino acid composition
Number of residues per
molecule of protein
Amino
Acid
Human
cytochrome c
Bovine
chymotrypsinogen
Ala
6
22
Arg
2
4
Asn
5
15
Asp
3
8
Cys
2
10
Gln
2
10
Glu
8
5
Gly
13
23
His
3
2
Ile
8
10
Number of residues per
molecule of protein
Amino
Acid
Human
cytochrome c
Bovine
chymotrypsinogen
Leu
6
19
Lys
18
14
Met
3
2
Phe
3
6
Pro
4
9
Ser
2
28
Thr
7
23
Trp
1
8
Tyr
5
4
Val
3
23
Total
104
245
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General properties of proteins
3. Frequency of amino acid composition
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General properties of proteins
4. Proteins can include other chemical
groups in addition to amino acids
Class
Prosthetic
group
Example
Lipoprotein
Lipids
b1-lipoprotein (blood)
Glycoprotein
Carbohydrates
(sugars)
Immunoglobulin G
(blood)
Phosphoprotein
Phosphate
groups
Casein (milk)
Hemoprotein
Heme (iron
porphyrin)
Hemoglobin
Flavoprotein
Flavin
nucleotides
Succinate
dehydrogenase
Metalloprotein
Fe
Zn
Ca
Cu
Ferritin
Alcohol dehydrogenase
Calmodulin
Plastocyanin
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General properties of proteins
5. Proteins have a specific shape
Globular proteins
Fibrillar (rod-like) proteins
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