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重译“呼吸的起源”
The Origin of Breathing
呼吸的起源
By Zach Zorich
作者：Zach Zorich
August 04, 2004 | Ancient Life
大约35亿年前，一种被现代人称为LUCA的生物逐渐具备了从周围环境吸入氧气的能力（LUCA是英文“地球上所有生物最后的共同祖先”的缩写）。吸氧功能的产生堪称划时代的化工奇迹，虽然LUCA早已灭绝，但夏威夷大学的微生物学家Maqsudul Alam还是在揭示这一奥秘方面取得了进展。
Some 3.5 billion years ago, a single-celled organism now named LUCA (for the Last Universal Common Ancestor of all life on Earth) developed the ability to pull oxygen out of its environment. Although LUCA is long gone, University of Hawaii microbiologist Maqsudul Alam has taken a step toward understanding the secret behind this world-changing feat of chemical engineering.
LUCA最初在无氧或缺氧的环境中进化。随着海洋与大气中氧含量的增加，氧实际上成为细胞的毒物，细胞必须以某种方式中和氧的毒性才能生存。Alam在研究archaea（另一种远古单细胞生物）时偶然发现了细胞的对抗氧损害防御机制。他同时研究了需氧型和厌氧型的Archaea。
LUCA evolved in an oxygen-free, or anaerobic, environment. But as oxygen levels rose in the ocean and atmosphere, the cell had to develop a way to neutralize what was, in essence, a poison. Alam hit on that defense while studying archaea—another type of primitive, single-celled creature. Alam studied two species of archaea, one aerobic and the other anaerobic.
他分离出一种叫protoglobin的重要物质，protoglobin能保护厌氧型Archaea免受氧的毒害。“protoglobin就象archaea的手和鼻子，”Alam说，“它能在氧对细胞造成伤害以前感觉到氧、与氧结合、把氧转移到细胞外”。显然，是Protoglobin或者类似物对LUCA起到了相似的保护作用。
He isolated a crucial compound called protoglobin that protects anaerobic species of archaea from the toxic effects of oxygen. “Protoglobin is the nose and the hand of the archaea,” he says. “It senses oxygen, binds it, and removes it from the cell before it can do any harm.” Protoglobin, or something much like it, apparently provided a similar defense for LUCA.
事实还不只这些。Alam纯化了Protoglobin来研究它的结构，这时他发现Protoglobin分子与稀释过的血液惊人的相似。事实上，Protoglobin能在某些部位结合氧气并在释放到其他部位，这与血红蛋白在血液中输送氧的方式一样。
But that is only half of the story. When Alam purified the protoglobin to study its structure, he saw that the molecule looks surprisingly like diluted blood. In fact, protoglobin binds and releases oxygen the same way that hemoglobin does as it transports oxygen through blood.
Alam相信，LUCA最初进化生成了protoglobin以保护自身免受氧的毒害，它的后代则进化生成了另一种分子：血色素。血色素使氧从有毒物转变成了营养物质。Alam说：血色素的出现使生命能在新环境中生存，从而为有氧呼吸生物的出现奠定了基础。
Alam believes that while LUCA initially evolved protoglobin for protection from oxygen, the organism’s descendants developed a variant of the molecule—hemoglobin—that transformed oxygen from a poison into a nutrient. That innovation enabled life to expand into new environments and set the stage for all oxygen-breathing organisms, Alam says.
下一步的工作是建立一个计算机模型来解释protoglobin的工作机理。Alam希望能通过这个模型揭示导致protoglobin形成的基因变化，并回答他所谓的“6400万美圆的问题”：Protoglobin经历了怎样的进化过程，从而能在多细胞或生物体内运输氧气。
The next step is to create a computer model that will explain how protoglobin works. Alam hopes such a model will allow him to unravel the genetic changes that transformed protoglobin and answer what he calls the $64 million question: How did protoglobin evolve to transport oxygen through the bodies of multicellular organisms? 呼吸的起源
作者：Zach Zorich
大约35亿年前，一种被现代人称为LUCA的生物逐渐具备了从周围环境吸入氧气的能力（LUCA是英文“地球上所有生物最后的共同祖先”的缩写）。吸氧功能的产生堪称划时代的化工奇迹，虽然LUCA早已灭绝，但夏威夷大学的微生物学家Maqsudul Alam还是在揭示这一奥秘方面取得了进展。
LUCA最初在无氧或缺氧的环境中进化。随着海洋与大气中氧含量的增加，氧实际上成为细胞的毒物，细胞必须以某种方式中和氧的毒性才能生存。Alam在研究archaea（另一种远古单细胞生物）时偶然发现了细胞的对抗氧损害防御机制。他同时研究了需氧型和厌氧型的Archaea。
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作者:admin@医学,生命科学 2011-02-18 12:58
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