Friday, January 28, 2011

DNA caught rock 'n rollin'

DNA, that marvelous, twisty molecule of life, has an alter ego, research at the University of Michigan and the University of California, Irvine reveals.

On rare occasions, its building blocks "rock and roll," deforming the familiar double helix into a different shape.

"We show that the simple DNA double helix exists in an alternative form—for one percent of the time—and that this alternative form is functional," said Hashim M. Al-Hashimi, who is the Robert L. Kuczkowski Professor of Chemistry and Professor of Biophysics at U-M. "Together, these data suggest that there are multiple layers of information stored in the genetic code." The findings were published online Jan. 26 in the journal Nature.

It's been known for some time that the DNA molecule can bend and flex, something like a rope ladder, but throughout these gyrations its building blocks—called bases—remain paired up just the way they were originally described by James Watson and Francis Crick, who proposed the spiral-staircase structure in 1953. By adapting nuclear magnetic resonance (NMR) technology, Al-Hashimi's group was able to observe transient, alternative forms in which some steps on the stairway come apart and reassemble into stable structures other than the typical Watson-Crick base pairs. ...

Because critical interactions between DNA and proteins are thought to be directed by both the sequence of bases and the flexing of the molecule, these excited states represent a whole new level of information contained in the genetic code, Al-Hashimi said. ...

via DNA caught rock 'n rollin'.

... A Hoogsteen base pair is a variation of base-pairing in nucleic acids such as the A•T pair. In this manner, two nucleobases on each strand can be held together by hydrogen bonds in the major groove. A Hoogsteen base pair applies the N7 position of the purine base (as a hydrogen bond acceptor) and C6 amino group (as a donor), which bind the Watson-Crick (N3–N4) face of the pyrimidine base.

- via Wikipedia

We are so complicated.

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