This new enzyme is considered a ribozyme because it is made from RNA. The RNA World hypothesis has many scientists suspecting that self-replicating RNA molecules were the precursors to life. The new ribozyme works in this way. It is self-replicating but it does not make a copy that is completely identical to itself. Instead, the copy is a mirror image of itself. This mirror image copy is then what makes a copy of the original ribozyme. This ribozyme is considered to be "cross-chiral" because of its replication abilities. The study shows that this type of enzyme could have been in existence during the RNA world and would have been the "key obstacle to the origin of life."
The "right-handed" original RNA are called D-RNA. The similarity in their structures is what makes interactions between them more efficient. It is the same as with a handshake; two right hands or two left hands are more efficient than a right and a left hand. "Scientists generally are taught to think that there has to be a common chirality among interacting molecules for biology to work," Joyce said.
Early Earth would have had a mixture of both of these right and left-handed forms. However, a study done by Joyce himself many years before showed that self-replicators would have had a hard time evolving in a mix like this. RNA strands would have gathered stray nucleotides that would eventually be incorporated into the strand and would, in turn, change the handedness and block any further assembly of that copy. One theory explains how a right-handed RNA enzyme could potentially make copies of other right-handed RNA molecules while ignoring left-handed L-RNA. Joyce has created such enzymes in the laboratory. These types of RNA have sticky base pairs that hamper its ability to copy other RNA molecules.
A "general-purpose" RNA replication enzyme has a lesser grip on the RNA it handles which explains how RNA and DNA can replicate without forming base pairs of the nucleic acids that they're copying. The question now is how could RNA like this work in early earth. The researchers thought that perhaps opposite-handed RNA would work because they are chemically prohibited from forming base pairs. "We started thinking: it feels a little weird but you can shake the wrong hand of somebody else," said Joyce.
This study resulted in the first ever attempt to make a ribozyme that worked cross-chirally, on opposite-handed RNA. Another member of the study, Jonathan T. Sczepanski used "test-tube evolution" to come up with this a ribozyme like this. The process began with a type of "soup" of about a quadrillion short RNA molecules with random sequences and right-handed chirality. "We set it up so that the molecules that could catalyze a joining reaction with left-handed RNA could be pulled out of solution and then amplified," Sczepanski said. Ten "selection-and-amplification" rounds were performed until a strong candidate ribozyme was found. The size of its core region was then expanded and put through six more rounds of selection to trim down the extraneous nucleotides. The end result was an 83-nucleotide ribozyme that was moderately sequence-specific and could comfortable "knit a test segment of left-handed RNA to a template" which is about one million times faster than what would have happened without enzyme assistance.
This new ribozyme can work without hindrance even when RNA nucleotides that are same-handed are present. It can now catalyze the assembly of 11 segments of RNA to make a copy of the left-handed opposite ribozyme which can then go on and make segments of right-handed RNA.
This article is very interesting and important in understanding the origin of life on Earth. I actually found this very interesting to read because the actual process of what the researchers did was thoroughly explained and seemed really cool. The new ribozyme they created is going to be very important in further studies and the method the researchers used to find it will definitely become more popular and will help find more enzymes that could potentially be very useful.
Article: http://www.sciencedaily.com/releases/2014/10/141029141216.htm
Related Article: http://www.dailymail.co.uk/sciencetech/article-2812903/Origins-life-Earth-explained-new-enzyme-created-TEST-TUBE.html
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