Download - Chapter 4 Chemistry of Protein 第四章 蛋白质化学
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Chapter 4 Chemistry of Protein
第四章 蛋白质化学
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主 要 内 容• Protein 的分子组成• Protein 的分子结构• Protein 结构与功能的关系• Protein 的理化性质
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• 什么是蛋白质 ( protein) ?自然界约 150 余万种生物体中,约有 101
0 ~ 1012 种蛋白质 ; 人体中大约 105 种。
X 衍射法 -- 晶体 --10 余年。世界上最大 PDB 到 2002 年 7 月 23 日存有 18294 种蛋白质的构象数据。
道尔顿 Dalton, Da:
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第一节 Protein 的化学组成
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一、 Protein 的元素 element 组成• 元素 element 构成: 碳—— 50%-55% 氢—— 6%-7% 氧—— 13%-19% Nitrogen (N) ——13%-19% 硫—— 0%-4% 其他——• The relation between N content and t
otal protein : mgPr=mgN×6.25
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二、氨基酸 amino acids(AA) 的化学结构
R
HH2N C
COOH1. Configuration of AA——L - type
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⒉ AA 的碳原子编号—— α-AA
H2N-CH2-CH2-CH2-CH2-CH-COOH
NH2
12¦Á
3¦Â
4¦Ã
5¦Ä
6¦Å
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三、 Classes of AA标准氨基酸 R 结构与极性 非极性疏水 R
极性不带电荷 R
带正电荷 R
带负电荷 R
R 结构 脂肪 / 芳香 / 杂环族
溶液酸碱性 酸性 / 碱性 / 中性人体能否合成异生成糖或酮
必需 / 非必需生糖 / 生酮 / 兼性
非标准氨基酸
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★ 非极性疏水 R-AA
H
H
COOH
NH2 C
CH3
H
COOH
NH2 C
CH2
H
CH
COOH
NH2 C
CH3
CH3
CH2
H
CH2
S
CH3
COOH
NH2 C H
CH2
CH3
CH3H
COOH
NH2 C
C CH2
H
COOH
NH2 C
CH2
H
NH
COOH
NH2 C
COOH
CH2
HN HC
COOH
NH2
CH
CH3 CH3
HC
CH2
CH
甘氨酸 丙氨酸 缬氨酸 脯氨酸
甲硫氨酸 异亮氨酸 亮氨酸 苯丙氨酸 色氨酸
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★ 极性不带电荷 R-AA
CH2
H
OH
COOH
NH2 C
CH2OH
H
COOH
NH2 C
CH2
H
NH2
O
COOH
NH2 C
C
CH2
H
CH2
NH2
O
COOH
NH2 C
C
H
CH3
OHH
COOH
NH2 C
C
H
SH
COOH
NH2 C
CH2
酪氨酸 天冬酰胺 谷氨酰胺
丝氨酸 苏氨酸 半胱氨酸
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★ 带正电荷 R-AA (Basic AA)
CH2
H
CH2
CH2
CH2
NH2
COOH
NH2 C
CH2
H
CH2
CH2
NH
NH2
NH
COOH
NH2 C
C
N
N
CH2
H
COOH
NH2 C
赖氨酸 精氨酸 组氨酸
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★ 带负电荷 R-AA (Acidic AA)
CH2
H
COOH
NH2 C
COOH
CH2
H
CH2
COOH
NH2 C
COOH
天冬氨酸 谷氨酸
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★ Essential AA and non-essential AAEAA NEAAVal Gly Leu Ala Ile Ser
Met Cys Thr 苏 Glu Lys Asp Phe Gln
Trp 色 Asn *His Pro *Arg Tyr 酪
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★ Non-standard AA• 羟脯氨酸• 羟赖氨酸• N-甲基赖氨酸• 硒代半胱氨酸• 胱氨酸• γ-羧基谷氨酸• 鸟氨酸、瓜氨酸
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四、 Classes of Protein• By components:
simple protein: albumin, globin
conjugated protein:
lipoprotein, glycoprotein, ribonucleoprotein • By source:
animal/vegetable/microorganism protein• By configuration:
fibrous protein, globular protein
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第二节 Chemical structure of protein
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• 一级结构 primary structure• 二级结构 secondary structure • 三级结构 tertiary structure• 四级结构 quaternary structure
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• 基本概念: 游离氨基酸 free AA, FAA
氨基酸残基 AA residue
肽键 peptide bond :刚性作用 肽平面 / 单元 peptide plane/unit
寡肽 oligopeptide
多肽 / 链 polypeptide/chain
N- 端 N-terminal/C- 端 C-terminal
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NH2 CH
O
OHC
R 1
N CH
O
OHH
H
C
R 2
N CH
O
OH
H
CNH2 CH
O
C
R 1 R 2
H2O
+
肽键
N
O
H
CC C
CC
N
O
H
CC C
O
N
H
C¦Á
¦Á
¦Ä-
¦Ä+
¦Á¦Á
¦Á¦Á+
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谷胱甘肽 Glutathione, GSH
HOOC-CH-CH2-CH2-C-NH-CH-C-NH-CH2-COOH
NH2 O CH2
SH
O
¦Ã-Glu Cys Gly
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Two peptides
H2N-Cys-Tyr- -Gln-Asn-Cys-Pro- -Gly-C-NH2
Ile Leu
Phe Arg
H2N-Cys-Tyr- -Gln-Asn-Cys-Pro- -Gly-C-NH2
O
O
S-S
S-S
催产素
加压素
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H
N N N N
H O
H
H O
H CH2
H O
H
H
CH3
O
H CH2OH
H
CH3
COOHNH2 C C C C C C C C C
SH
氨基端 羧基端多肽链
N-terminal and C-terminal
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• Chemical bonds holding protein configuration: peptide bond disulfide bond 氢键 hydrogen bond 疏水作用 hydrophobic interaction 离子键 ionic bond 范德华力 Van der Waals interaction
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一、 Primary structure• Definition : The linear sequence of a
mino acids is the primary structure of a protein (including disulfide bridge).
• 生物学意义: 基础、病理、进化
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S S A链 I I Gly-Ile-Val-Glu-Gln-Cys-Cys-Ala-Ser-Val-Cys-Ser-Leu-Tyr-Gln-Leu-Glu-Asn-Tyr-Cys-Asn 5 I 10 15 I 21 S S I S S B链 I I Phe-Val-Asn-Gln-His-Leu-Cys-Gly-Ser-His-Leu-Val-Glu-Ala-Leu-Tyr-Leu-Val-Cys-Gly-Glu-Arg-Gly-Phe-Phe-Tyr-Thr-Pro-Lys-Ala 5 10 15 20 25 30
_________
• Bovine insulin 是第一个阐明 P. S. 的 protein ,也是第一个人工合成的 protein 。它含 A 、 B 两条 peptide chains , A 链有21 个 AA residues , B 链有 30 个 AA residues ,此外含 6 个 Cys ,构成 3 个 disulfide bridges ,其中 2 个在 A 、 B 链之间,A 链内还有 1 个 disulfide bridge 。
• 牛胰岛素 bovine insulin
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二、 Secondary structure • Definition : Secondary structure is a local r
egular occuring structure in proteins and is mainly formed through hydrogen bonds between backbone atoms.
• So-called random coils 无规则卷曲 , loops 环状结构 or turns 转角 don't have a stable secondary structure. There are two types of stable secondary structures: Alpha helix(α- 螺旋 ) and beta-sheet (β- 折叠 ).
• Alpha-helix and beta-sheet are preferably located at the core of the protein, whereat loops prefer to reside in outer regions.
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α-H
elix
的结构模型
• right-handed• 3.6 aa per turn• hydrogen bond N-H···O=C
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同向β-S
heet
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反向β-S
heet
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β-Turn
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• 超二级结构 super secondary structure:
又称模体 / 基元 motif 。 αα/ααα
βαβ
βββ
α- 转角 -α
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三、 Tertiary structure
• Definition: Tertiary structure describes the more compact packing of alpha-helices, beta-sheets and random coils with respect to each other on the level of one whole polypeptide chain.
• 结构域 domain:
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肌红蛋白
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肌红蛋白
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四、quaternary structure
• Definition: In biochemistry, quaternary structure is the arrangement of multiple folded protein molecules in a multi-subunit complex.
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血红蛋白
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血红蛋白
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四种结构的比较:
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第三节 Structure and Function of Protein
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• Primary structure & Function
• Dimensional structure & Function
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第四节 Chemicophysical Properties
of Protein
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• 一般性质: 紫外吸收 ultraviolet absorption
呈色反应 chromogenic reaction
两性电离 amphipathic ionization
等电点 isoelectric point, pI
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Ultraviolet absorption of AA and protein
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茚三酮 chromogenic reaction(AA)
O
O
OH
OH
O
O
OH
H
O
OOH
O
N+ NH3 + + H2O
还原茚三酮 水合茚三酮 蓝紫色化合物
O
O
OH
OHR-CH-COOH
NH2
CH
O
O
OH
H
水合茚三酮 氨基酸 还原茚三酮
+ + NH3 + CO2 + R-CHO
O.D570
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• Protein 双缩脲反应: peptide bond 硫酸铜 紫色或红色 检测 protein 水解程度
• Protein 的 Lowry 反应: Folin- 酚试剂 蓝色复合物
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amphipathic ionization and pI of AA and protein
R
HNH3
+
O
OC
C
O
H
OH
NH2
R
C
C
R
HNH3
+
O
OHC
C
R
HH2N
O
OC
C
非电离形式
兼性离子pH £¼pI pH £½pI pH £¾pI
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• 大分子特性: Protein 溶液是胶体 colloid 溶液 沉淀 precipitation
电泳 electrophoresis
透析 dialysis
超速离心 ultracentrifugation
/ 沉降 sedimentation
沉降系数 S——1S=10-13 秒 变性 denaturation
复性 renaturation
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核酸酶变性实验
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核酸酶复性实验
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BRIEF SUMMARY
• Relation between N content and total protein
• AA 分类• Protien 的结构• Protien 的性质: