メタロチオネインの二重ナノモラーとピコモラーZn (II) 結合特性
1Department of Preventive Medicine and Community Health, The University of Texas Medical Branch, Galveston, Texas 77555, USA.
Journal of the American Chemical Society
|August 19, 2007
まとめ
メタロチオニンは,亜鉛イオンを様々な親和性で結合させ,細胞内の亜鉛の可用性を調節する. アポプロテインであるチオネインは,亜鉛の放出を制御し,チオールの反応性と生物学的プロセスに影響を与えます.
科学分野:
- バイオケミストリー バイオケミストリー
- メタロタンパク質化学 メタロタンパク質化学
- 細胞亜鉛ホメオスタシス ホメオスタシス
背景:
- 人間のメタロチオネインは,Zn(3) S(9) とZn(4) S(11) のクラスター内のテトラチオラート協調環境で7つのZn(II) イオンを含んでいます.
- メタロチオニンは,細胞の亜鉛バッファリングと解毒に重要な役割を果たします.
研究 の 目的:
- チオニン (アポプロテイン) とメタロチオニンとのZn(II) イオンの結合親和性を調査する.
- メタロチオニンとチオニンの細胞内の自由亜鉛濃度とチオール反応性の調節における役割を明らかにする.
主な方法:
- チオネインとZn(II) の関連と,光合合合剤 (FluoZin-3とRhodZin-3) を使用したメタルチオネインからの解離の分析.
- Zn(II) 結合親近性の決定 (表面ログK) と,異なる Zn(II) 結合種 (Zn(4) T から Zn(7) T) の特徴付け.
主要な成果:
- メタロチオネインに結合するZn (II) は,少なくとも3つの種類のサイトを4つの大きさによって異なる親和度で表しています.
- 4つのZn(II) イオンは緊密に結合している (log K ≈ 11.8),一方1つは弱い結合している (log K ≈ 7.7),メタロチオニンが亜鉛ドナーとして作用することを可能にします.
- 細胞濃度において優位な種はZn(5) TとZn(6) T (log K ≈10) である. チオネインは,自由Zn (II) レベルを調節し,チオールの酸化速度に影響を与えます.
結論:
- メタロチオニエインの独特なZn (II) 結合親和性は,強力なケレーターおよび亜鉛ドナーとして機能することを可能にします.
- チオネインとメタロチオネインの比率は,自由なZn (pZn) レベルを決定的に制御し,細胞の要求に一致します.
- メタロチオニンとチオニンの分子構造とリドックス化学は,重要な生物学的プロセスのためのZn (II) の可用性を決定する.
関連する概念動画
02:51Metal-Ligand Bonds
The hemoglobin in the blood, the chlorophyll in green plants, vitamin B-12, and the catalyst used in the manufacture of polyethylene all contain coordination compounds. Ions of the metals, especially the transition metals, are likely to form complexes.
In these complexes, transition metals form coordinate covalent bonds, a kind of Lewis acid-base interaction in which both of the electrons in the bond are contributed by a donor (Lewis base) to an electron acceptor (Lewis acid). The Lewis acid in...
In these complexes, transition metals form coordinate covalent bonds, a kind of Lewis acid-base interaction in which both of the electrons in the bond are contributed by a donor (Lewis base) to an electron acceptor (Lewis acid). The Lewis acid in...
01:07Ladder Diagrams: Complexation Equilibria
Ladder diagrams are useful for evaluating equilibria involving metal-ligand complexes. The vertical scale of the ladder diagram represents the concentration of unreacted or free ligand, pL. The horizontal lines on the scale depict the log of stepwise formation constants for metal-ligand complexes and indicate the dominant species in all the regions.
The formation constant, K1, for the formation of Cd(NH3)2+ complex from cadmium and ammonia is 3.55 × 102. Log K1 (i.e. pNH3) is 2.55, and...
The formation constant, K1, for the formation of Cd(NH3)2+ complex from cadmium and ammonia is 3.55 × 102. Log K1 (i.e. pNH3) is 2.55, and...
01:09Complexation Equilibria: Factors Influencing Stability of Complexes
In complexation reactions, metal cations are the electron pair acceptors, and the ligands are the electron pair donors. The stability of the metal complexes depends primarily on the complexing ability of the central metal ion and the nature of the ligands. Generally, the complexing ability of the metal ion depends on the size and charge of the ion. As the metal ion size increases, the stability of the metal complexes decreases, provided that the valency of the metal ion and the ligands remain...
03:45Formation of Complex Ions
A type of Lewis acid-base chemistry involves the formation of a complex ion (or a coordination complex) comprising a central atom, typically a transition metal cation, surrounded by ions or molecules called ligands. These ligands can be neutral molecules like H2O or NH3, or ions such as CN− or OH−. Often, the ligands act as Lewis bases, donating a pair of electrons to the central atom. These types of Lewis acid-base reactions are examples of a broad subdiscipline called coordination...
03:02Colors and Magnetism
Color in Coordination Complexes
When atoms or molecules absorb light at the proper frequency, their electrons are excited to higher-energy orbitals. For many main group atoms and molecules, the absorbed photons are in the ultraviolet range of the electromagnetic spectrum, which cannot be detected by the human eye. For coordination compounds, the energy difference between the d orbitals often allows photons in the visible range to be absorbed and emitted, which is seen as colors by the human eye.
When atoms or molecules absorb light at the proper frequency, their electrons are excited to higher-energy orbitals. For many main group atoms and molecules, the absorbed photons are in the ultraviolet range of the electromagnetic spectrum, which cannot be detected by the human eye. For coordination compounds, the energy difference between the d orbitals often allows photons in the visible range to be absorbed and emitted, which is seen as colors by the human eye.
00:43Complexometric Titration: Ligands
Different monodentate and polydentate ligands are used as complexing agents in complexometric titration reactions. The formation of complexes by mono- and bidentate ligands involves two or more intermediate steps, limiting their use as complexing agents. In comparison, polydentate ligands can form complexes with metal ions in a single-step process, facilitating sharper end points. This means polydentate ligands, such as amino carboxylic acid derivatives, are most commonly employed in...