科研之友
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摘要
Metallothionein (MT) is a ubiquitous protein with a low molecular weight of 6-7 kDa weight and it was first identified in the kidney cortex of equines as a cadmium (Cd)-binding protein responsible for the natural accumulation of Cd in the tissue. The mammalian MT contains 61 to 68 amino acid residues, in which 18 to 23 cysteine residues are present. The expression of MT starts by binding of metal transcription factor-1 (MTF-1) to the regulative region of MT gene called metal responsive elements (MREs). The induction of MT through the MREs region can be initiated by several metal ions such as zinc (Zn), copper (Cu) and Cd. However, Zn is the only heavy metal which can reversibly and directly activate the DNA-binding activity of MTF-1. In mammals four types of MT are expressed and they are termed metallothionein-1 (MT1), metallothionein-2 (MT2), metallothionein-3 (MT3), and metallothionein-4 (MT4). MT1 and MT2 are expressed in almost all tissues while MT3 and MT4 are tissue-specific. MT is a key compound involved in the intracellular handling of a variety of essential and nonessential post-transitional metal ions. In order to the heavy metal binding ability of MT, it is suggested to play roles both in the intracellular fixation of essential trace elements Zn and Cu, in controlling the concentrations, and in neutralizing the harmful influences of exposure to toxic elements. Metalotioneina (MT) es una prote赤na, con bajo peso molecular de kDa 6-7 y que fue primero identificada en la corteza renal de equinos como cadmio (Cd)-prote赤na responsable por la acumulaci車n natural de Cd en los tejidos. La MT en mam赤feros contiene 61 a 68 residuos de amino芍cidos, de los cuales est芍n presentes 18 a 23 residuos de ciste赤na. La expresi車n de MT se inicia por la uni車n del factor-1 de transcripci車n de metal (MTF-1) a la regi車n reguladora del gen de la MT llamado elementos met芍licos responsable (MREs). La inducci車n de MT a trav谷s de la regi車n MREs puede ser iniciada por varios iones met芍licos tales como zinc (Zn), cobre (Cu) y Cd. Sin embargo, el Zn es el 迆nico metal pesado que puede revertir y activar directamente la uni車n ADN de MTF-1. En los mam赤feros se expresan cuatro tipos de MT y ellos se denominan metalotione赤na-1 (MT1), metalotione赤na-2 (MT2), metalotione赤na-3 (MT3), y metalotione赤na-4 (MT4). MT1 y MT2 se expresan en casi todos los tejidos mientras que MT3 y MT4 son tejido-espec赤fico. La MT es un compuesto clave implicado en la manipulaci車n intracelular de una variedad de iones met芍licos esenciales y no esenciales post-transicionales. Con el fin de evaluar la capacid
