Monday's Molecule #75

 
Some readers have been complaining that Monday's Molecule is too easy.¹ That's why I've chosen a more difficult task for you today.

You have to examine the structure and figure out what's going on. The molecule you have to identify isn't even shown in the figure—only small fragments are depicted. You need to identify the invisible molecule and explain why this figure is so important. Its importance is mostly historical. The elucidation of what's happening is a defining moment in biochemistry and helped open up a whole new field of study.

There's a direct connection between today's molecule and a Nobel Prize. The prize was awarded for discovering exactly what the figure depicts. The first person to correctly identify the molecule, describe what the figure shows, and name the Nobel Laureate(s), wins a free lunch at the Faculty Club. Previous winners are ineligible for one month from the time they first collected the prize. There are three ineligible candidates for this week's reward.

THEME:

Nobel Laureates
Send your guess to Sandwalk (sandwalk (at) bioinfo.med.utoronto.ca) and I'll pick the first email message that correctly identifies the molecule and names the Nobel Laureate(s). Note that I'm not going to repeat Nobel Laureate(s) so you might want to check the list of previous Sandwalk postings by clicking on the link in the theme box. [Hint: A co-recipient of this week's Nobel Laureates is already on the list.]

Correct responses will be posted tomorrow. I may select multiple winners if several people get it right. (Like that's going to happen this week!)

Comments will be blocked for 24 hours. Comments are now open.

UPDATE: Turns out it wasn't as difficult as I thought. The winning answer arrived within one hour, followed shortly by several other correct answers. The image shows a small piece of RNA about to be cleaved in the active site of Ribonuclease A. The key residues are His12, His119, and Lys 41 and their interactions with the substrate are shown. Note how they form weak interactions with the phosphodiester linkage. This causes destabilization of the bonds in preparation for cleavage. The Nobel Laureates are Stanford Moore and William Stein who received the Nobel Prize in 1972 for working out the mechanism of Ribonuclease A. This was the first detailed demonstration of how enzymes worked at the molecular level.

The winner is Michael Clarkson. Congratulations Michael.

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1. Okay, maybe not "some" readers. Maybe it's only one reader. In fact, maybe I'm the reader.