Genome complexity: Z-DNA a new layer of complexity (Introduction)

by David Turell , Friday, July 09, 2021, 19:13 (1021 days ago) @ David Turell

More study on the bacteriophage with this strange DNA:

https://phys.org/news/2021-07-biosynthesis-pathway-dna-nucleobase-elucidated.html

"...in a bacteriophage, another base, represented by the letter Z, exists. This exception, the only one observed to date, has long remained a mystery. Scientists from the Institut Pasteur and the CNRS, in collaboration with the CEA, have now elucidated the biosynthesis pathway of this base.

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"Cyanophage S-2L is a bacteriophage, in other words a virus that infects bacteria. In this phage, adenine is completely replaced by another base, 2-aminoadenine (represented by the letter Z). The latter forms three hydrogen bonds with thymine (Z-T), instead of the usual two bonds between adenine and thymine. This higher number of bonds increases the stability of the DNA at high temperatures and changes its conformation, meaning that the DNA is less well recognized by proteins and small molecules.

"Since it was discovered in 1977, cyanophage S-2L has been the only known exception, and the biosynthesis pathway of 2-aminoadenine has remained unknown. Scientists from the Institut Pasteur and the CNRS, in collaboration with the CEA, recently elucidated this biosynthesis pathway and demonstrated its enzymatic origins. They achieved this by identifying a homolog of the known enzyme succinoadenylate synthase (PurA) in the genome of cyanophage S-2L. A phylogenetic analysis of this enzyme family revealed a link between the homolog, known as PurZ, and the PurA enzyme in archaea. This indicates that the homolog is an ancient enzyme that probably conferred an evolutionary advantage. The research was carried out using the Institut Pasteur's Crystallography Platform.

"The new Z-T base pair and the discovery of the biosynthesis pathway show that new bases can be enzymatically incorporated into genetic material."

Comment: It needs a special enzyme. As I've always noted, enzymes are giant specialize molecules which are hard to imagine appearing by chance. It still suggests design. See this previous entry: Friday, April 30, 2021, 20:05