A TINY genetic change can transform the function of an enzyme, scientists who captured the forces of natural selection in a Petri dish have shown. Their experiment is the first demonstration of how families of genes can evolve within living organisms.
Inside every cell is a complicated metabolic factory where specific proteins act as enzymes, converting available molecules into compounds vital for the life of the cell. A key question for evolutionary biologists is how this complicated machinery arose.
One theory is that genes in the simple genomes of early life forms duplicated, leaving the second copy of the gene free to take on a new function. If a mutation occurred that helped the organism survive, the new gene would be adopted and preserved. 快猫短视频s believe that related gene families are the result of this process happening over and over again, generating new and specific metabolic pathways.
Advertisement
No one had ever shown this happening in living organisms, but now scientists at the University of Florence, Italy, have proved just how easy it is for enzymes to take on new identities. Renato Fani and Matteo Brilli started with two related genes that produce enzymes involved in different stages of the synthesis of histidine, an amino acid crucial for bacteria to function. They knocked out one gene, so the bacteria could survive only if given histidine from an outside source. Then they took away the histidine. 鈥淭he cells either mutate or die,鈥� says Fani.
By adding a spare copy of the functional gene, the scientists gave the bacteria a way to cheat death. If a mutation allowed this copy to perform the function of the gene that was knocked out, the bugs would recreate their ability to synthesise histidine.
Some bacteria did survive. 鈥淭he research shows that an enzyme can spontaneously mutate back to what it was,鈥� comments bioinformaticist William Collis. 鈥淚t鈥檚 amazing that one point mutation can change the structure and function of an enzyme.鈥�
Fani and Brilli are now checking the exact mutations that saved the bacteria. Preliminary tests have ruled out any major changes, narrowing it down to single amino acid changes or tiny insertions or deletions in the gene.
