A basic discovery

Scientists find the 22nd amino acid

Published: Sunday 30 June 2002

scientists have recently discovered the 22nd amino acid, the building blocks of proteins that carry out the functions of a living cell. This is a significant discovery that would enable scientists to manipulate the human genetic code to make proteins to speed chemical reactions. The amino acid was discovered by us-based Ohio State University researchers.

The new amino acid has been named pyrrolysine. Genes are composed of dna, a molecule made of pairs of chemicals called bases which are known by the letters a, c, g and t (adenine, cytosine, guanine and thymine). When the hereditary instructions in a gene are carried out, the dna's code is transcribed into rna, which is made of bases a, c, g and u (uracil). The code within the rna is used three bases at a time for making the proteins that carry out every function in a living cell.

When rna's instructions are used to make a protein, three bases order production to start, and three bases, known as a 'stop codon', signal that the protein is complete. Researchers found that the three rna bases u, a and g don't always act to signal that a protein is complete. They instead can be reprogrammed to act as the genetic blueprint for pyrrolysine.

They discovered the genetic code for pyrrolysine in microbes called Methanosarcina barkeri, which produce methane or natural gas. The microbes belong to the group of organisms known as archaea , which are single-celled organisms that tend to live in extreme environments such as hot springs. According to researchers, their discovery raises the bigger question of how life's genetic code is reprogrammed to do new things. It also suggests that there may be other surprises out there.

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