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使用一種不被自然利用的稀有金屬,，萊斯大學的化學家們發(fā)明了一種合成酶,，有助于解開難以研究的數千種蛋白質的身份，其中包括許多在癌癥和其他疾病發(fā)揮關鍵角色的蛋白質,。這項研究zui近在線發(fā)表在《美國化學學會雜志》上,。

“我們已經將銠的化學性能和目前生物學已知能識別和選擇的特定蛋白結合在一起，"共同研究作者Zachary Ball,，萊斯大學化學助理教授說,，“結果是一種工具，在許多方面,，比任何單獨使用生物或化學的方法更有效,。"

Ball三年前開始研究雙銠催化劑。他一開始沒有試圖用它們們來合成酶,，但他對一個研究產生了興趣,，雙銠催化劑可用于修飾色氨酸，后者是構成生命基本組成部分的21種氨基酸其中之一,。

催化劑增加反應速率而促進化學反應,，而自己不被消耗。在生物體內,，稱為酶的蛋白質發(fā)揮同樣的功能,。但不同于許多無機催化劑，酶是非常具有選擇性的,。在生物學家常常比作 “鎖和鑰匙"的過程中,，酶只和分子形狀與之配對的分子相作用，這可以避免整個細胞產生無關的反應,。

Ball和博士后研究員Brian Popp想知道酶反應的選擇性是否可以和銠基催化劑相結合,。他們對設想進行了驗證，通過將催化劑連接到到能與其他蛋白質結合在一起的蛋白質的部分區(qū)域,，形如一條纖維束,。這種“卷曲螺旋"包裝模式在生物學中常見，尤其是在信號蛋白中,。信號蛋白是那些能激活或失活諸如凋亡的關鍵過程的蛋白,，“程序性死亡"在癌癥中發(fā)揮關鍵作用,。

“信號通路猶如多米諾骨牌，"Ball說,， “數十種蛋白質參與其中,，它們相互作用形成級聯(lián)反應。在大多數情況下,，相互作用短暫和微弱,，很難用傳統(tǒng)方法觀察到，因此我們對于關鍵信號蛋白在健康和疾病發(fā)揮的作用還不清楚,。"

Ball說,，他和Popp合成酶的策略可能有助于解決這一問題。在他們的試驗中,，化學家能夠開發(fā)出可以選擇性地與蛋白質結合的合成酶,，并進行標記，以便讓生物學家能識別它們,。

除色氨酸外,，用同樣的方法研究了苯丙氨酸和酪氨酸，它們是信號蛋白質中兩個2個常見的氨基酸,。zui近尚未發(fā)表的研究表明,，這個研究策略可能在更多氨基酸中起效。

巴爾說,，這個過程必須加以完善,，才能在大多數生物實驗室中使用，但他和Popp已經為實現該戰(zhàn)略廣泛應用而努力,。

該研究由韋爾奇基金會和萊斯大學資助,。

Synthetic Enzymes Could Help ID Proteins 
Using a rare metal that's not utilized by nature, Rice University chemists have created a synthetic enzyme that could help unlock the identities of thousands of difficult-to-study proteins, including many that play key roles in cancer and other diseases.

The research was recently published online in the Journal of the American Chemical Society.

"We have combined the chemical capabilities of rhodium with what biology already knows about recognizing and selecting specific proteins," said study co-author Zachary Ball, assistant professor of chemistry at Rice. "The result is a tool that, in many ways, is more powerful than any biological or chemical approach alone."

Ball began studying dirhodium catalysts more than three years ago. He did not start out trying to create enzymes with them, but he was intrigued by a study that showed dirhodium catalysts could be used to modify tryptophan, one of the 21 amino acids that are the basic building blocks of life.

Catalysts enhance chemical reactions by increasing the rate of reaction without being consumed themselves. In living things, proteins called enzymes serve the same purpose. But unlike many inorganic catalysts, enzymes are very selective. In a process that biologists often liken to a "lock and key," enzymes associate only with molecules that match their shape exactly. This prevents them from spurring extraneous reactions throughout the cell.

Ball and postdoctoral research associate Brian Popp wondered if they could marry the selectivity of enzymatic reactions with a rhodium-based catalyst. They tested the idea by attaching their catalyst to a short segment of protein that can wrap with other proteins, like strands of rope fiber. This "coiled coil" wrapping motif is common in biology, particularly in signaling proteins. Signaling proteins are those that activate or deactivate key processes like apoptosis, the "programmed death" response that's known to play a key role in cancer.

"Signaling pathways are like a trail of dominos," Ball said. "Dozens of proteins can be involved, and they interact one after the other in a cascade. In most cases, the interactions are both fleeting and weak. They are difficult to observe with traditional methods, and as a result we are still in the dark about the roles that key signaling proteins play in health and disease."

Ball said his and Popp's synthetic enzyme strategy might help solve that problem. In their tests, the chemists were able to develop synthetic enzymes that could selectively bind with proteins and attach tags that would allow biologists to identify them.

In addition to tryptophan, the method worked with phenylalanine and tyrosine, two amino acids commonly found in signaling proteins. And recent unpublished studies indicate the researchers' strategy might work for even more amino acids.

Ball said the process must be refined before it can be used in the majority of biology labs, but he and Popp are already working toward realizing broad applications of the strategy.

The research was funded by the Welch Foundation and Rice University.