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Struc­tural Grace II

by Elio

Photo by José M. Sogo. Source

In her au­to­bi­og­ra­phy in the 2007 An­nual Re­view of Mi­cro­biology, Mar­garita Salas pub­lished an elec­tron mi­crograph of rare beauty. It shows the DNA of phage Φ29 ca­su­ally coiled around it­self, with pro­tein TP (for Ter­mi­nal Pro­tein) at the two ends. Not only is this a fine demon­stration of a spe­cific DNA-pro­tein in­ter­ac­tion, but the sur­pris­ingly sym­met­ri­cal spi­ral of the DNA in­vites spe­culation about how it coiled it­self so el­e­gantly. Any ideas?

 

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Autumn Cochrane
18 years ago

I have a the­ory as to how it could have coiled up. As­sum­ing that this does not hap­pen in every cell, may be it was the way in which the hy­dro­gen bonds hap­pened to line up. See­ing that it is DNA and all, DNA likes to coil up, thanks to hy­dro­gen bond­ing. It seems to me that this could very well be the an­swer. In an ad­di­tion to my guess, may be the ma­nip­u­la­tion re­quired in prepar­ing the DNA for EM al­lowed the hy­dro­gen bonds to line up in just the right way to pro­duce this im­age. In any case, an­a­lyza­tion aside, it is beau­ti­ful and stun­ningly con­cen­tric.

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